Two-dimensional(2D)fully compensated collinear magnetic materials ofer signifcant advantages for spintronic applications,including robustness against magnetic feld perturbations,no stray felds,and ultrafast dynamics.A...Two-dimensional(2D)fully compensated collinear magnetic materials ofer signifcant advantages for spintronic applications,including robustness against magnetic feld perturbations,no stray felds,and ultrafast dynamics.Among these materials,fully compensated ferrimagnets are particularly promising due to their unique characteristics such as the magneto-optical efect,completely spin-polarized currents,and the anomalous Hall efect.We performed a structural search on 2D unconventional stoichiometric Cr-I crystals using a global optimization algorithm.The most stable CrI-P21/m monolayer is a fully compensated ferrimagnetic semiconductor with a band gap of 1.57 eV and a high magnetic transition temperature of 592 K.The spontaneous spin splitting in CrI-P21/m originates from the inequivalent local coordination environments of Cr^(1)and Cr^(2)ions,yielding a mismatch in their 3d orbitals splitting.Notably,carrier doping at a concentration of 0.01 electrons or holes per atom enables reversible spin polarization,generating a fully spin-polarized current in CrI-P21/m.This performance makes it a highly promising candidate for spintronic devices.Our fndings not only provide a structural paradigm for discovering fully compensated ferrimagnets but also open a new avenue for designing zero-moment magnetic materials with intrinsic spin splitting.展开更多
3d transition metal chalcogenides have attracted much attention due to their unique magnetic properties.Although various Cr,V,and Fe-based chalcogenides have been fabricated recently,the limited Curie temperature(T_C)...3d transition metal chalcogenides have attracted much attention due to their unique magnetic properties.Although various Cr,V,and Fe-based chalcogenides have been fabricated recently,the limited Curie temperature(T_C)still hinders their practical application.Based on the structural and magnetic advantages of MFe_(2)O_(4)and Fe_(3)Se_(4),we developed a one-pot solution synthesis method for the fabrication of NiFe_(2)Se_(4)nanostructures with structural continuity,to facilitate the investigation of their magnetic properties.Notably,the morphology of Ni Fe_(2)Se_(4)can be controlled from nano-rods to nano-platelets by controlling the growth direction.The coercivity(H_(C))of NiFe_(2)Se_(4)with nano-cactus structure exhibits a maximum of 12.77kOe at 5 K.The coercivity of ferrimagnetic NiFe_(2)Se_(4)nano-platelets can be further adjusted to 1.52 kOe at room temperature.These results show that the magnetic properties of NiFe_(2)Se_(4)can be significantly modified by controlling their morphologies.We also extend the method to the synthesis of Co Fe_(2)Se_(4)nano-cactus with an ultrahigh coercivity of 17.85 k Oe at 5 K.Obviously,the synthesis strategy and their excellent magnetic properties of MFe_(2)Se_(4)have sparked interest in ternary transition metal selenides as potential hard magnetic materials.展开更多
Cubic Mn_(2)Ru_(x)Ga Heusler compound is a typical example of compensated ferrimagnet with attractive potential for high-density,ultrafast,and low-power spintronic applications.In the form of epitaxial thin films,Mn_(...Cubic Mn_(2)Ru_(x)Ga Heusler compound is a typical example of compensated ferrimagnet with attractive potential for high-density,ultrafast,and low-power spintronic applications.In the form of epitaxial thin films,Mn_(2)Ru_(x)Ga exhibits high spin polarization and high tunability of compensation temperature by freely changing the Ru content x in a broad range(0.3<x<1.0).Herein Mn-Ru-Ga-based polycrystalline bulk buttons prepared by arc melting are systematically studied and it is found that in equilibrium bulk form,the cubic structure is unstable when x<0.75.To overcome this limitation,Mn-Ru-Ga is alloyed with a fourth element V.By adjusting the content of V in the By adjusting the content of V in the Mn_(2)Ru_(0.75)V_(y)Ga and Mn_(2.25-y)Ru_(0.75)V_(y)Ga quaternary systems the magnetic compensation temperature is tuned.Compensation is achieved near 300 K which is confirmed by both the magnetic measurement and anomalous Hall effect measurement.The analyses of the anomalous Hall effect scaling in quaternary Mn-Ru-V-Ga alloy reveal the dominant role of skew scattering,notably that contributed caused by the thermally excited phonons,in contrast to the dominant intrinsic mechanism found in many other 3d ferromagnets and Heusler compounds.It is further shown that the Ga antisites and V content can simultaneously control the residual resistivity ratio(RRR)as well as the relative contribution of phonon and defect to the anomalous Hall effect a"/a0'in Mn-Ru-V-Ga,resulting in a scaling relation a"/a0'∝RRR^(1.8).展开更多
The multisublattice Green＇s function technique is applied to study the magnetic properties of a mixed spin-2 and spin-5/2 Heisenberg ferrimagnetic system on a two-dimensional honeycomb lattice. The role of the differ...The multisublattice Green＇s function technique is applied to study the magnetic properties of a mixed spin-2 and spin-5/2 Heisenberg ferrimagnetic system on a two-dimensional honeycomb lattice. The role of the different interactions in the Hamiltonian is explored. When only the nearest-neighbor interaction and the single-ion anisotropy are included, our results indicate that there are compensation points at finite temperatures. When the next-nearest-neighbor interaction exceeds a minimum value that depends on the other parameters in the Hamiltonian, the compensation point disappears. The next-nearest-neighbor interaction has the effect of changing the compensation temperature.展开更多
Ferrimagnets, which contain the advantages of both ferromagnets(detectable moments) and antiferromagnets(ultrafast spin dynamics), have recently attracted great attention. Here, we report the optimization of epitaxial...Ferrimagnets, which contain the advantages of both ferromagnets(detectable moments) and antiferromagnets(ultrafast spin dynamics), have recently attracted great attention. Here, we report the optimization of epitaxial growth of a tetragonal perpendicularly magnetized ferrimagnet Mn_(2)Ga on MgO. Electrical transport, magnetic properties and the anomalous Hall effect(AHE) were systematically studied. Furthermore, we successfully integrated high-quality epitaxial ferrimagnetic Mn_(2)Ga thin films onto ferroelectric 0.7PbMg_(1/3)Nb_(2/3)O_(3)–0.3PbTiO_(3) single crystals with a MgO buffer layer. It was found that the AHE of such a ferrimagnet can be effectively modulated by a small electric field over a large temperature range in a nonvolatile manner. This work thus demonstrates the great potential of ferrimagnets for developing high-density and low-power spintronic devices.展开更多
Rare earth iron garnets R3Fe5-xMnxO12（R=Pr, Nd, Sm, Eu） were prepared through mild hydrothermal me- thod. The initial alkalinity of solutions was thought to play an important role in governing the content of Mn. The...Rare earth iron garnets R3Fe5-xMnxO12（R=Pr, Nd, Sm, Eu） were prepared through mild hydrothermal me- thod. The initial alkalinity of solutions was thought to play an important role in governing the content of Mn. The effect of substitution Fe^3＋ ions by Mn^3＋ ions on magnetic properties was investigated. The saturation magnetizations of Mn-doped samples are larger than that of corresponding parent compounds due to the moment of Mn^3＋ ion being smaller than that of Fe^3＋. It is clearly shown that incorporation of Mn^3＋ gives rise to significant variations in the Curie temperature. With increasing of Mn content x, Curie temperatures reduced sharply for the garnets, which could be explained by the exchange interaction between a-d Fe^3＋ being reduced in these compounds.展开更多
We use the mean-field approximation of Dyson–Maleev representation to study an XXZ Heisenberg ferrimagnetic spin chain with single-ion anisotropy. By solving the self-consistent equations with different anisotropies,...We use the mean-field approximation of Dyson–Maleev representation to study an XXZ Heisenberg ferrimagnetic spin chain with single-ion anisotropy. By solving the self-consistent equations with different anisotropies, λ and D respectively,the energy spectrums, internal energy, static susceptibility and specific heat are calculated. Especially, the quantum phase transition of the magnetization plateau induced by single-ion anisotropy D is obtained in the model of the ferrimagnetic spin chain by using Dyson–Maleev mean-field theory.展开更多
Magnetic hyperthermia is a fast emerging, non-invasive cancer treatment method which is used synergistically with the existing cancer therapeutics. We have attempted to address the current challenges in clinical magne...Magnetic hyperthermia is a fast emerging, non-invasive cancer treatment method which is used synergistically with the existing cancer therapeutics. We have attempted to address the current challenges in clinical magnetic hyperthermia-improved biocompatibility and enhanced heating characteristics, through a single combinatorial approach. Both superparamagnetic iron oxide nanoparticles(SPIONs) of size 10 nm and ferrimagnetic iron oxide nanoparticles(FIONs) of size 30 nm were synthesized by thermal decomposition method for comparison studies. Two different surface modifying agents, viz, Cetyl Trimethyl Ammonium Bromide and 3-Aminopropyltrimethoxysilane, were used to conjugate Bovine Serum Albumin(BSA) over the iron oxide nanoparticles via two different methods—surface charge adsorption and covalent amide bonding, respectively. The preliminary haemolysis and cell viability experiments show that BSA conjugation mitigates the haemolytic effect of the iron oxide nanoparticles on erythrocytes and is non-cytotoxic to the healthy Baby Hamster Kidney cells. It was observed from the results that due to better colloidal stability, the SAR value of the BSA-iron oxide nanoparticles is higher than the iron oxide nanoparticles without BSA, irrespective of the size of the iron oxide nanoparticles and method of conjugation. The BSA-FIONs seem to show improved biocompatibility, as the haemolytic index is less than 2 % and cell viability is up to 120 %, when normalized with the control. The SAR value of BSAFIONs is 2300 Wg^(-1) when compared to 1700 Wg^(-1) of FIONs without BSA conjugation. Thus, we report here that BSA conjugation over FIONs(with a high saturation magnetization of 87 emug^(-1)) provide a single combinatorial approach to improve the biocompatibility and enhance the SAR value for magnetic hyperthermia, thus addressing both the current challenges of the same.展开更多
Magnetic properties of a two sublattice ferrimagnet with antiferromagnetic exchange interaction inside one of the sublattices are calculated within the framework of the molecular field theory taking into account the a...Magnetic properties of a two sublattice ferrimagnet with antiferromagnetic exchange interaction inside one of the sublattices are calculated within the framework of the molecular field theory taking into account the anisotropy of unstable sublattice. The magnetization curves of single crystal GdMn 2Ge 2 for the magnetic field parallel and perpendicular to the c axis at different temperatures are calculated. Field induced magnetic phase transitions in GdMn 2Ge 2 are discussed. Calculated H T magnetic phase diagrams are in fair agreement with experimental data.展开更多
We use the Schwinger-boson approach to study the anisotropy ferrimagnetic spin-（1/2,1） chain with bond alternation.Based on the effect of bond alternation δ,we obtain energy gap,free energy,and specific heat,respec...We use the Schwinger-boson approach to study the anisotropy ferrimagnetic spin-（1/2,1） chain with bond alternation.Based on the effect of bond alternation δ,we obtain energy gap,free energy,and specific heat,respectively.The specific heat with larger bond alternation（δ 〉 0.7） displays a peak at low temperature.Based on the effect of XXZ anisotropy parameter Δ,we present excited spectrums,free energy,and specific heat,respectively.展开更多
We have investigated the low-temperature magnetism and spin-lattice coupling in （Bio.46Nao.46Bao.os）TiO3 ：Co in order to understand the magnetoelectric effect in such artificially synthesized dilute magnetic ferroe...We have investigated the low-temperature magnetism and spin-lattice coupling in （Bio.46Nao.46Bao.os）TiO3 ：Co in order to understand the magnetoelectric effect in such artificially synthesized dilute magnetic ferroelectrics. It is revealed that the as-prepared （Bio.46Nao.46Bao.os）TiO3：Co at Co content of 20%~30% exhibits fascinating ferrimagnetism which is robust against magnetic field, the abnormal spin lattice coupling characterized by a negative magnetostriction effect; and the suppressed magnetic moment within the temperature range of 30 K-50 K is identified. These magnetic behaviours at low temperatures can be explained by the competition between the ferrimagnetic response and the magnetic moment suppression induced by the abnormal spin lattice coupling effect. Finally, the ferroelectric and magnetodielectric properties are also discussed.展开更多
The ferrimagnetism and quantum phase transition of a bipartite lozenge periodic Anderson-like organic polymer, in which the localized f electrons hybridize with the odd site conduction orbitals, are investigated by me...The ferrimagnetism and quantum phase transition of a bipartite lozenge periodic Anderson-like organic polymer, in which the localized f electrons hybridize with the odd site conduction orbitals, are investigated by means of Green＇s function theory. The ground state turns out to be gapless ferrimagnetism. At a finite temperature, the ferrimagnetic-to- paramagnetic phase transition takes place. The Kondo screenings and Ruderman-Kittel-Kasuya-Yosida （RKKY） inter- action can reduce and increase the transition temperature, respectively. Two Kondo screenings compete with each other, giving rise to the localized f electron spin screened antiferromagnetically. Accordingly, in a magnetic field, all spins are aligned along the chain easily, which is associated with metal-insulator transition. Furthermore, in a temperature-field plane, we reveal the gapless and spin polarized phases, which are characterized by susceptibility and specific heat, and whose behaviours are determined by the competition between the up-spin and down-spin hole excitations.展开更多
The magnetic properties of an antiferromagnetic bond alternating spin-l/2 zigzag chain with asymmetrical ferro- magnetic next-nearest-neighbour exchange interactions at finite temperature are investigated by using the...The magnetic properties of an antiferromagnetic bond alternating spin-l/2 zigzag chain with asymmetrical ferro- magnetic next-nearest-neighbour exchange interactions at finite temperature are investigated by using the many-body Green＇s function theory. It is found that the ferrimagnetic ordering does not appear in the symmetrical next-nearest- neighbour coupling case, and takes place only for the asymmetrical next-nearest-neighbour case at finite temperature rather than the ground state. Furthermore, as the asymmetry degree of the next-nearest-neighbour exchange inter- actions increases, the ferrimagnetism becomes more and more dominant. It is shown that the elementary excitation spectra are responsible for the observed magnetic behaviour.展开更多
The electronic structures of Ti_2NbSb with Hg_2CuTi structure and TiZrNbSb with LiMgPdSn structure are investigated using first-principles calculations.The results indicate that Ti_2NbSb is a fully compensated ferrima...The electronic structures of Ti_2NbSb with Hg_2CuTi structure and TiZrNbSb with LiMgPdSn structure are investigated using first-principles calculations.The results indicate that Ti_2NbSb is a fully compensated ferrimagnetic spin-gapless semiconductor with an energy gap of 0.13 e V,and TiZrNbSb is a half-metallic fully compensated ferrimagnet with a half-metallic gap of 0.17 e V.For Ti_2NbSb,the total energy of the Hg_2CuTi structure is0.62 e V/f.u.higher than that of the L2_(1) structure,which is the ground state,and for TiZrNbSb,the total energy of the structure considered in this work is only 0.15 e V/f.u.larger than that of the ground state.Thus both of them may be good candidates for spintronic applications.展开更多
We conducted a comparative study of the magnetic and transport properties of single-crystalline LaCo_(2)As_(2) and NdCo_(2)As_(2).LaCo_(2)As_(2) is a soft metallic ferromagnet which exhibits purely intrinsic anomalous...We conducted a comparative study of the magnetic and transport properties of single-crystalline LaCo_(2)As_(2) and NdCo_(2)As_(2).LaCo_(2)As_(2) is a soft metallic ferromagnet which exhibits purely intrinsic anomalous Hall effect(AHE) due to Co-3d electrons. With Nd-4f electronic magnetism, ferrimagnetic NdCo_(2)As_(2) manifests pronounced sign reversal and multiple hysteresis loops in temperature-and field-dependent magnetization, Hall resistivity, and magnetoresistance, due to complicated magnetic structural changes. We reveal that the AHE for NdCo_(2)As_(2) is stemming from the Co sub-lattice and deduce its phase diagram which includes magnetic compensation and two meta-magnetic phase transitions. The sensitivity of the Hall effect on the details of the magnetic structures in ferrimagnetic NdCo_(2)As_(2) provides a unique opportunity to explore the magnetic interaction between 4f and 3d electrons and its impact on the electronic structure.展开更多
Spin-wave theory is used to study magnetic properties of ferromagnetic double layers with a ferrimagnetic interlayer coupling at zero temperature. The spin-wave spectra and four sublattices magnetizations and internal...Spin-wave theory is used to study magnetic properties of ferromagnetic double layers with a ferrimagnetic interlayer coupling at zero temperature. The spin-wave spectra and four sublattices magnetizations and internal energy are calculated by employing retarded Green function technique. The sublattice magnetizations at ground state are smaller than their classical values, owing to the zero-point quantum fluctuations of the spins.展开更多
Compensated ferrimagnetic insulators are particularly interesting for enabling functional spintronic,optical,and microwave devices.Among many different garnets,Gd_(3)Fe_(5)O_(12)(GdIG)is a representative compensated f...Compensated ferrimagnetic insulators are particularly interesting for enabling functional spintronic,optical,and microwave devices.Among many different garnets,Gd_(3)Fe_(5)O_(12)(GdIG)is a representative compensated ferrimagnetic insulator.In this paper,we will study the evolution of the surface morphology,the magnetic properties,and the magnetization compensation through changing the following parameters:the annealing temperature,the growth temperature,the annealing duration,and the choice of different single crystalline garnet substrates.Our objective is to find the optimized growth condition of the GdIG films,for the purpose of achieving a strong perpendicular magnetic anisotropy(PMA)and a flat surface,together with a small effective damping parameter.Through our experiments,we have found that the surface roughness approaching 0.15 nm can be obtained by choosing the growth temperature around 700℃,together with an enhanced PMA.We have also found the modulation of magnetic anisotropy by choosing different single crystalline garnet substrates which change the tensile strain to the compressive strain.A measure of the effective magnetic damping parameter(α_(eff)=0.04±0.01)through a spin pumping experiment in a GdIG/Pt bilayer is also made.Through optimizing the growth dynamics of GdIG films,our results could be useful for synthesizing garnet films with a PMA,which could be beneficial for the future development of ferrimagnetic spintronics.展开更多
In this work,we study the domain wall motion in ferrimagnet driven by a circularly polarized magnetic field using the collective coordinate theory and atomistic micromagnetic simulations,and we pay particular attentio...In this work,we study the domain wall motion in ferrimagnet driven by a circularly polarized magnetic field using the collective coordinate theory and atomistic micromagnetic simulations,and we pay particular attention to the effect of Dzyaloshinskii-Moriya interaction(DMI).Similar to the case of antiferromagnetic domain wall,ferrimagnetic wall moves at a speed which is linearly dependent on the DMI magnitude.In addition,it is revealed that the DMI plays a role in modulating the domain wall dynamics similar to that of the net spin density,which suggests another internal parameter for controlling domain wall in ferrimagnets.Moreover,the results show that the domain wall dynamics in ferrimagnets is much faster than that in ferromagnets,which confirms again the great potential of ferrimagnets in future spintronic applications.展开更多
The spin Hall magnetoresistance(SMR)effect in Pt/Gd_(3)Fe_(5)O_(12)(Gd IG)bilayers was systematically investigated.The sign of SMR changes twice with increasing magnetic field in the vicinity of the magnetization comp...The spin Hall magnetoresistance(SMR)effect in Pt/Gd_(3)Fe_(5)O_(12)(Gd IG)bilayers was systematically investigated.The sign of SMR changes twice with increasing magnetic field in the vicinity of the magnetization compensation point(TM)of Gd IG.However,conventional SMR theory predicts the invariant SMR sign in the heterostructure composed of a heavy metal film in contact with a ferromagnetic or antiferromagnetic film.We conclude that this is because of the significant enhancement of the magnetic moment of the Gd sub-lattice and the unchanged moment of the Fe sub-lattice with a relatively large field,meaning that a small net magnetic moment is induced at TM.As a result,the Néel vector aligns with the field after the spin-flop transition,meaning that a bi-reorientation of the Néel vector is produced.Theoretical calculations based on the Néel’s theory and SMR theory also support our conclusions.Our findings indicate that the Néel-vector direction of a ferrimagnet can be tuned across a wide range by a relatively low external field around TM.展开更多
Topological crystalline insulator(TCI)SnTe is a potential material for quantum electronic devices because of its attractive inherent sensitivity of band topology and highly mobile characteristic of Dirac fermions.The ...Topological crystalline insulator(TCI)SnTe is a potential material for quantum electronic devices because of its attractive inherent sensitivity of band topology and highly mobile characteristic of Dirac fermions.The proximity effect at the interface of SnTe film can affect the topological surface transport and may result in novel quantum magneto-electric effects.Here,we study the magnetoelectrical transport properties of SnTe thin films grown on ferrimagnetic insulators Eu_3Fe_5O_(12)(110)(EuIG(110))and Y_(3)Fe_(5)O_(12)(111)(YIG(111))single-crystal underlayers by molecular beam epitaxy.Linear magnetic resistance(LMR)is observed in SnTe/Eu IG heterostructures in the low field range,which is different from the weak antilocalization(WAL)characteristic of SnTe/YIG heterostructures.Especially,the double carrier characteristic with the coexistence of holes and electrons in SnTe/Eu IG heterostructure is quite different from the holes as main carriers in SnTe/YIG,although the SnTe layer remains the same crystal plane(100)in the two heterostructures.The LMR in SnTe/Eu IG is attributed to the topological surface Dirac electrons and disordered domain distribution in the SnTe layer which is in sharp contrast to the WAL of SnTe/YIG with ordered domain distribution in the SnTe layer.The present studies of transport properties not only provide a fundamental understanding of the transport mechanism of TCI and magnetite insulator heterostructure but also display the promising application probability for tunable topological electronic devices.展开更多
基金supported by the Natural Science Foundation of Wenzhou Institute,University of Chinese Academy of Sciences(UCAS)(Grant No.WIUCASQD2023004)the National Natural Science Foundation of China(Grant Nos.12304006,12404265,and 12435001)+2 种基金the Natural Science Foundation of Shanghai,China(Grant No.23JC1401400)the Natural Science Foundation of Wenzhou(Grant No.L2023005)the Fundamental Research Funds for the Central Universities of East China University of Science and Technology。
文摘Two-dimensional(2D)fully compensated collinear magnetic materials ofer signifcant advantages for spintronic applications,including robustness against magnetic feld perturbations,no stray felds,and ultrafast dynamics.Among these materials,fully compensated ferrimagnets are particularly promising due to their unique characteristics such as the magneto-optical efect,completely spin-polarized currents,and the anomalous Hall efect.We performed a structural search on 2D unconventional stoichiometric Cr-I crystals using a global optimization algorithm.The most stable CrI-P21/m monolayer is a fully compensated ferrimagnetic semiconductor with a band gap of 1.57 eV and a high magnetic transition temperature of 592 K.The spontaneous spin splitting in CrI-P21/m originates from the inequivalent local coordination environments of Cr^(1)and Cr^(2)ions,yielding a mismatch in their 3d orbitals splitting.Notably,carrier doping at a concentration of 0.01 electrons or holes per atom enables reversible spin polarization,generating a fully spin-polarized current in CrI-P21/m.This performance makes it a highly promising candidate for spintronic devices.Our fndings not only provide a structural paradigm for discovering fully compensated ferrimagnets but also open a new avenue for designing zero-moment magnetic materials with intrinsic spin splitting.
基金supported by the National Natural Science Foundation of China(Nos.51971122,52371191,52301244)the National Key R&D Program of China(No.2022YFB3505301)。
文摘3d transition metal chalcogenides have attracted much attention due to their unique magnetic properties.Although various Cr,V,and Fe-based chalcogenides have been fabricated recently,the limited Curie temperature(T_C)still hinders their practical application.Based on the structural and magnetic advantages of MFe_(2)O_(4)and Fe_(3)Se_(4),we developed a one-pot solution synthesis method for the fabrication of NiFe_(2)Se_(4)nanostructures with structural continuity,to facilitate the investigation of their magnetic properties.Notably,the morphology of Ni Fe_(2)Se_(4)can be controlled from nano-rods to nano-platelets by controlling the growth direction.The coercivity(H_(C))of NiFe_(2)Se_(4)with nano-cactus structure exhibits a maximum of 12.77kOe at 5 K.The coercivity of ferrimagnetic NiFe_(2)Se_(4)nano-platelets can be further adjusted to 1.52 kOe at room temperature.These results show that the magnetic properties of NiFe_(2)Se_(4)can be significantly modified by controlling their morphologies.We also extend the method to the synthesis of Co Fe_(2)Se_(4)nano-cactus with an ultrahigh coercivity of 17.85 k Oe at 5 K.Obviously,the synthesis strategy and their excellent magnetic properties of MFe_(2)Se_(4)have sparked interest in ternary transition metal selenides as potential hard magnetic materials.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1402600)the National Natural Science Foundation of China(Grant No.12274438)the Beijing Natural Science Foundation,China(Grant No.Z230006)。
文摘Cubic Mn_(2)Ru_(x)Ga Heusler compound is a typical example of compensated ferrimagnet with attractive potential for high-density,ultrafast,and low-power spintronic applications.In the form of epitaxial thin films,Mn_(2)Ru_(x)Ga exhibits high spin polarization and high tunability of compensation temperature by freely changing the Ru content x in a broad range(0.3<x<1.0).Herein Mn-Ru-Ga-based polycrystalline bulk buttons prepared by arc melting are systematically studied and it is found that in equilibrium bulk form,the cubic structure is unstable when x<0.75.To overcome this limitation,Mn-Ru-Ga is alloyed with a fourth element V.By adjusting the content of V in the By adjusting the content of V in the Mn_(2)Ru_(0.75)V_(y)Ga and Mn_(2.25-y)Ru_(0.75)V_(y)Ga quaternary systems the magnetic compensation temperature is tuned.Compensation is achieved near 300 K which is confirmed by both the magnetic measurement and anomalous Hall effect measurement.The analyses of the anomalous Hall effect scaling in quaternary Mn-Ru-V-Ga alloy reveal the dominant role of skew scattering,notably that contributed caused by the thermally excited phonons,in contrast to the dominant intrinsic mechanism found in many other 3d ferromagnets and Heusler compounds.It is further shown that the Ga antisites and V content can simultaneously control the residual resistivity ratio(RRR)as well as the relative contribution of phonon and defect to the anomalous Hall effect a"/a0'in Mn-Ru-V-Ga,resulting in a scaling relation a"/a0'∝RRR^(1.8).
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10574048 and 20490210
文摘The multisublattice Green＇s function technique is applied to study the magnetic properties of a mixed spin-2 and spin-5/2 Heisenberg ferrimagnetic system on a two-dimensional honeycomb lattice. The role of the different interactions in the Hamiltonian is explored. When only the nearest-neighbor interaction and the single-ion anisotropy are included, our results indicate that there are compensation points at finite temperatures. When the next-nearest-neighbor interaction exceeds a minimum value that depends on the other parameters in the Hamiltonian, the compensation point disappears. The next-nearest-neighbor interaction has the effect of changing the compensation temperature.
基金the National Natural Science Foundation of China(Nos.52121001,51822101,51861135104 and 51771009)。
文摘Ferrimagnets, which contain the advantages of both ferromagnets(detectable moments) and antiferromagnets(ultrafast spin dynamics), have recently attracted great attention. Here, we report the optimization of epitaxial growth of a tetragonal perpendicularly magnetized ferrimagnet Mn_(2)Ga on MgO. Electrical transport, magnetic properties and the anomalous Hall effect(AHE) were systematically studied. Furthermore, we successfully integrated high-quality epitaxial ferrimagnetic Mn_(2)Ga thin films onto ferroelectric 0.7PbMg_(1/3)Nb_(2/3)O_(3)–0.3PbTiO_(3) single crystals with a MgO buffer layer. It was found that the AHE of such a ferrimagnet can be effectively modulated by a small electric field over a large temperature range in a nonvolatile manner. This work thus demonstrates the great potential of ferrimagnets for developing high-density and low-power spintronic devices.
基金Supported by the National Natural Science Foundation of China(Nos.90922034,20771042)
文摘Rare earth iron garnets R3Fe5-xMnxO12（R=Pr, Nd, Sm, Eu） were prepared through mild hydrothermal me- thod. The initial alkalinity of solutions was thought to play an important role in governing the content of Mn. The effect of substitution Fe^3＋ ions by Mn^3＋ ions on magnetic properties was investigated. The saturation magnetizations of Mn-doped samples are larger than that of corresponding parent compounds due to the moment of Mn^3＋ ion being smaller than that of Fe^3＋. It is clearly shown that incorporation of Mn^3＋ gives rise to significant variations in the Curie temperature. With increasing of Mn content x, Curie temperatures reduced sharply for the garnets, which could be explained by the exchange interaction between a-d Fe^3＋ being reduced in these compounds.
基金Project supported by the National Natural Science Foundation of China(Grant No.10774035)the Qianjiang RenCai Program of Zhejiang Province,China(Grant No.2007R0010)
文摘We use the mean-field approximation of Dyson–Maleev representation to study an XXZ Heisenberg ferrimagnetic spin chain with single-ion anisotropy. By solving the self-consistent equations with different anisotropies, λ and D respectively,the energy spectrums, internal energy, static susceptibility and specific heat are calculated. Especially, the quantum phase transition of the magnetization plateau induced by single-ion anisotropy D is obtained in the model of the ferrimagnetic spin chain by using Dyson–Maleev mean-field theory.
文摘Magnetic hyperthermia is a fast emerging, non-invasive cancer treatment method which is used synergistically with the existing cancer therapeutics. We have attempted to address the current challenges in clinical magnetic hyperthermia-improved biocompatibility and enhanced heating characteristics, through a single combinatorial approach. Both superparamagnetic iron oxide nanoparticles(SPIONs) of size 10 nm and ferrimagnetic iron oxide nanoparticles(FIONs) of size 30 nm were synthesized by thermal decomposition method for comparison studies. Two different surface modifying agents, viz, Cetyl Trimethyl Ammonium Bromide and 3-Aminopropyltrimethoxysilane, were used to conjugate Bovine Serum Albumin(BSA) over the iron oxide nanoparticles via two different methods—surface charge adsorption and covalent amide bonding, respectively. The preliminary haemolysis and cell viability experiments show that BSA conjugation mitigates the haemolytic effect of the iron oxide nanoparticles on erythrocytes and is non-cytotoxic to the healthy Baby Hamster Kidney cells. It was observed from the results that due to better colloidal stability, the SAR value of the BSA-iron oxide nanoparticles is higher than the iron oxide nanoparticles without BSA, irrespective of the size of the iron oxide nanoparticles and method of conjugation. The BSA-FIONs seem to show improved biocompatibility, as the haemolytic index is less than 2 % and cell viability is up to 120 %, when normalized with the control. The SAR value of BSAFIONs is 2300 Wg^(-1) when compared to 1700 Wg^(-1) of FIONs without BSA conjugation. Thus, we report here that BSA conjugation over FIONs(with a high saturation magnetization of 87 emug^(-1)) provide a single combinatorial approach to improve the biocompatibility and enhance the SAR value for magnetic hyperthermia, thus addressing both the current challenges of the same.
文摘Magnetic properties of a two sublattice ferrimagnet with antiferromagnetic exchange interaction inside one of the sublattices are calculated within the framework of the molecular field theory taking into account the anisotropy of unstable sublattice. The magnetization curves of single crystal GdMn 2Ge 2 for the magnetic field parallel and perpendicular to the c axis at different temperatures are calculated. Field induced magnetic phase transitions in GdMn 2Ge 2 are discussed. Calculated H T magnetic phase diagrams are in fair agreement with experimental data.
基金supported by the National Natural Science Foundation of China(Grant No.10774035)the Qianjiang RenCai Program of Zhejiang Province,China(Grant No.2007R0010)
文摘We use the Schwinger-boson approach to study the anisotropy ferrimagnetic spin-（1/2,1） chain with bond alternation.Based on the effect of bond alternation δ,we obtain energy gap,free energy,and specific heat,respectively.The specific heat with larger bond alternation（δ 〉 0.7） displays a peak at low temperature.Based on the effect of XXZ anisotropy parameter Δ,we present excited spectrums,free energy,and specific heat,respectively.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50832002 and 10874075)the National Basic Research Program of China (Grant Nos. 2009CB613303 and 2009CB929501)the Natural Science Foundation of Jiangsu Province,China (Grant No. BK2008024)
文摘We have investigated the low-temperature magnetism and spin-lattice coupling in （Bio.46Nao.46Bao.os）TiO3 ：Co in order to understand the magnetoelectric effect in such artificially synthesized dilute magnetic ferroelectrics. It is revealed that the as-prepared （Bio.46Nao.46Bao.os）TiO3：Co at Co content of 20%~30% exhibits fascinating ferrimagnetism which is robust against magnetic field, the abnormal spin lattice coupling characterized by a negative magnetostriction effect; and the suppressed magnetic moment within the temperature range of 30 K-50 K is identified. These magnetic behaviours at low temperatures can be explained by the competition between the ferrimagnetic response and the magnetic moment suppression induced by the abnormal spin lattice coupling effect. Finally, the ferroelectric and magnetodielectric properties are also discussed.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11204157 and 11174179)the China Three Gorges University Project (Grant No.KJ2011B068)the Yichang City Project,China (Grant No.A201230229)
文摘The ferrimagnetism and quantum phase transition of a bipartite lozenge periodic Anderson-like organic polymer, in which the localized f electrons hybridize with the odd site conduction orbitals, are investigated by means of Green＇s function theory. The ground state turns out to be gapless ferrimagnetism. At a finite temperature, the ferrimagnetic-to- paramagnetic phase transition takes place. The Kondo screenings and Ruderman-Kittel-Kasuya-Yosida （RKKY） inter- action can reduce and increase the transition temperature, respectively. Two Kondo screenings compete with each other, giving rise to the localized f electron spin screened antiferromagnetically. Accordingly, in a magnetic field, all spins are aligned along the chain easily, which is associated with metal-insulator transition. Furthermore, in a temperature-field plane, we reveal the gapless and spin polarized phases, which are characterized by susceptibility and specific heat, and whose behaviours are determined by the competition between the up-spin and down-spin hole excitations.
基金Project supported by the National Natural Science Foundation of China (Grant No.1010804034)the Science Foundation of China for Three Gorges University (Grant No.KJ2009B012)
文摘The magnetic properties of an antiferromagnetic bond alternating spin-l/2 zigzag chain with asymmetrical ferro- magnetic next-nearest-neighbour exchange interactions at finite temperature are investigated by using the many-body Green＇s function theory. It is found that the ferrimagnetic ordering does not appear in the symmetrical next-nearest- neighbour coupling case, and takes place only for the asymmetrical next-nearest-neighbour case at finite temperature rather than the ground state. Furthermore, as the asymmetry degree of the next-nearest-neighbour exchange inter- actions increases, the ferrimagnetism becomes more and more dominant. It is shown that the elementary excitation spectra are responsible for the observed magnetic behaviour.
基金Supported by the National Natural Science Foundation of China under Grant No 51301119the Natural Science Foundation for Young Scientists of Shanxi Province under Grant No 2013021010-1the Scientific and Technological Innovation Programs of Higher Education Institutions of Shanxi Province under Grant No 201802023
文摘The electronic structures of Ti_2NbSb with Hg_2CuTi structure and TiZrNbSb with LiMgPdSn structure are investigated using first-principles calculations.The results indicate that Ti_2NbSb is a fully compensated ferrimagnetic spin-gapless semiconductor with an energy gap of 0.13 e V,and TiZrNbSb is a half-metallic fully compensated ferrimagnet with a half-metallic gap of 0.17 e V.For Ti_2NbSb,the total energy of the Hg_2CuTi structure is0.62 e V/f.u.higher than that of the L2_(1) structure,which is the ground state,and for TiZrNbSb,the total energy of the structure considered in this work is only 0.15 e V/f.u.larger than that of the ground state.Thus both of them may be good candidates for spintronic applications.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB1502502)the National Natural Science Foundation of China(Grant Nos.12141002 and 12225401)+6 种基金the Fund from Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratorysupported by the Interdisciplinary Program of Wuhan National High Magnetic Field Center(Grant No.WHMFC202123)Huazhong University of Science and Technologysupported by the National Natural Science Foundation of China(Grant Nos.12074041 and 11674030)the Foundation of the National Key Laboratory of Shock Wave and Detonation Physics(Grant No.6142A03191005)the National Key Research and Development Program of China(Grant No.2016YFA0302300)the startup funding of Beijing Normal University。
文摘We conducted a comparative study of the magnetic and transport properties of single-crystalline LaCo_(2)As_(2) and NdCo_(2)As_(2).LaCo_(2)As_(2) is a soft metallic ferromagnet which exhibits purely intrinsic anomalous Hall effect(AHE) due to Co-3d electrons. With Nd-4f electronic magnetism, ferrimagnetic NdCo_(2)As_(2) manifests pronounced sign reversal and multiple hysteresis loops in temperature-and field-dependent magnetization, Hall resistivity, and magnetoresistance, due to complicated magnetic structural changes. We reveal that the AHE for NdCo_(2)As_(2) is stemming from the Co sub-lattice and deduce its phase diagram which includes magnetic compensation and two meta-magnetic phase transitions. The sensitivity of the Hall effect on the details of the magnetic structures in ferrimagnetic NdCo_(2)As_(2) provides a unique opportunity to explore the magnetic interaction between 4f and 3d electrons and its impact on the electronic structure.
基金supported by the Natural Science Foundation of Liaoning Province under Grant No.20041021the Scientific Foundation of the Educational Department of Liaoning Province under Grant Nos.2004C006 and 20060638the Postdoctoral Foundation of Shenyang University of Technology
文摘Spin-wave theory is used to study magnetic properties of ferromagnetic double layers with a ferrimagnetic interlayer coupling at zero temperature. The spin-wave spectra and four sublattices magnetizations and internal energy are calculated by employing retarded Green function technique. The sublattice magnetizations at ground state are smaller than their classical values, owing to the zero-point quantum fluctuations of the spins.
基金Project supported by the National Key R&D Program of China(Grant Nos.2017YFA0206200 and 2016YFA0302300)the Basic Science Center Project of the National Natural Science Foundation of China(Grant No.51788104)+2 种基金the National Natural Science Foundation of China(Grant Nos.11774194,11804182,51831005,and 11811082)Beijing Natural Science Foundation(Grant No.Z190009)the Beijing Advanced Innovation Center for Future Chip(ICFC).
文摘Compensated ferrimagnetic insulators are particularly interesting for enabling functional spintronic,optical,and microwave devices.Among many different garnets,Gd_(3)Fe_(5)O_(12)(GdIG)is a representative compensated ferrimagnetic insulator.In this paper,we will study the evolution of the surface morphology,the magnetic properties,and the magnetization compensation through changing the following parameters:the annealing temperature,the growth temperature,the annealing duration,and the choice of different single crystalline garnet substrates.Our objective is to find the optimized growth condition of the GdIG films,for the purpose of achieving a strong perpendicular magnetic anisotropy(PMA)and a flat surface,together with a small effective damping parameter.Through our experiments,we have found that the surface roughness approaching 0.15 nm can be obtained by choosing the growth temperature around 700℃,together with an enhanced PMA.We have also found the modulation of magnetic anisotropy by choosing different single crystalline garnet substrates which change the tensile strain to the compressive strain.A measure of the effective magnetic damping parameter(α_(eff)=0.04±0.01)through a spin pumping experiment in a GdIG/Pt bilayer is also made.Through optimizing the growth dynamics of GdIG films,our results could be useful for synthesizing garnet films with a PMA,which could be beneficial for the future development of ferrimagnetic spintronics.
基金financially supported by the National Natural Science Foundation of China(No.51971096)the National Natural Science Foundation of Guangdong Province(No.2019A1515011028)+1 种基金Guangdong Basic and Applied Basic Research Foundation(No.2022A1515011727)the National College Students'Innovation and Entrepreneurship Training Program(No.202110574049)。
文摘In this work,we study the domain wall motion in ferrimagnet driven by a circularly polarized magnetic field using the collective coordinate theory and atomistic micromagnetic simulations,and we pay particular attention to the effect of Dzyaloshinskii-Moriya interaction(DMI).Similar to the case of antiferromagnetic domain wall,ferrimagnetic wall moves at a speed which is linearly dependent on the DMI magnitude.In addition,it is revealed that the DMI plays a role in modulating the domain wall dynamics similar to that of the net spin density,which suggests another internal parameter for controlling domain wall in ferrimagnets.Moreover,the results show that the domain wall dynamics in ferrimagnets is much faster than that in ferromagnets,which confirms again the great potential of ferrimagnets in future spintronic applications.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0303202 and 2016YFA0300803)the National Natural Science Foundation of China(Grant Nos.11904194,11727808,and 11674159)the Fundamental Research Funds for the Central Universities,China(Grant No.020414380121)。
文摘The spin Hall magnetoresistance(SMR)effect in Pt/Gd_(3)Fe_(5)O_(12)(Gd IG)bilayers was systematically investigated.The sign of SMR changes twice with increasing magnetic field in the vicinity of the magnetization compensation point(TM)of Gd IG.However,conventional SMR theory predicts the invariant SMR sign in the heterostructure composed of a heavy metal film in contact with a ferromagnetic or antiferromagnetic film.We conclude that this is because of the significant enhancement of the magnetic moment of the Gd sub-lattice and the unchanged moment of the Fe sub-lattice with a relatively large field,meaning that a small net magnetic moment is induced at TM.As a result,the Néel vector aligns with the field after the spin-flop transition,meaning that a bi-reorientation of the Néel vector is produced.Theoretical calculations based on the Néel’s theory and SMR theory also support our conclusions.Our findings indicate that the Néel-vector direction of a ferrimagnet can be tuned across a wide range by a relatively low external field around TM.
基金financially supported by the National Natural Science Foundation of China(Nos.52071324,51871219,and 52031014)the National Key R&D Program of China(No.2017YFA0206301)。
文摘Topological crystalline insulator(TCI)SnTe is a potential material for quantum electronic devices because of its attractive inherent sensitivity of band topology and highly mobile characteristic of Dirac fermions.The proximity effect at the interface of SnTe film can affect the topological surface transport and may result in novel quantum magneto-electric effects.Here,we study the magnetoelectrical transport properties of SnTe thin films grown on ferrimagnetic insulators Eu_3Fe_5O_(12)(110)(EuIG(110))and Y_(3)Fe_(5)O_(12)(111)(YIG(111))single-crystal underlayers by molecular beam epitaxy.Linear magnetic resistance(LMR)is observed in SnTe/Eu IG heterostructures in the low field range,which is different from the weak antilocalization(WAL)characteristic of SnTe/YIG heterostructures.Especially,the double carrier characteristic with the coexistence of holes and electrons in SnTe/Eu IG heterostructure is quite different from the holes as main carriers in SnTe/YIG,although the SnTe layer remains the same crystal plane(100)in the two heterostructures.The LMR in SnTe/Eu IG is attributed to the topological surface Dirac electrons and disordered domain distribution in the SnTe layer which is in sharp contrast to the WAL of SnTe/YIG with ordered domain distribution in the SnTe layer.The present studies of transport properties not only provide a fundamental understanding of the transport mechanism of TCI and magnetite insulator heterostructure but also display the promising application probability for tunable topological electronic devices.
