The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity ex...The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity experiments. With an increase in the magnetic field H, the antiferromagnetic transition temperature TN is observed to shift progressively toward lower temperatures. The corresponding high temperature cubic （Fd3m） to low temperature tetragonal （I41amd） structural transition is tuned simultaneously due to the inherent strong spin-lattice coupling. In the antiferromagnetic phase, an anomaly at Hc2 defined as a steep downward peak in the derivative of the M-H curve is dearly drawn. It is found that TN versus H and Hc2 versus T exhibit a consistent tendency, indicative of a field-induced tetragonal （I41amd） to cubic （Fd3m） structural transition. The transition is further substantiated by the field-dependent dielectric constant and thermal conductivity measurements. We modify the T-H phase diagram, highlighting the coexistence of the paramagnetic state and ferromagnetic clusters between 100K and TN.展开更多
In the Temperature-Pressure phase diagram, the quasi-one-dimensional conductor, HMTSF-TCNQ, the ground state at ambient pressure is an insulator of charge density wave (CDW) below 30 K, while it shows a good metallic ...In the Temperature-Pressure phase diagram, the quasi-one-dimensional conductor, HMTSF-TCNQ, the ground state at ambient pressure is an insulator of charge density wave (CDW) below 30 K, while it shows a good metallic nature at higher temperature. The CDW insulating state is suppressed by a pressure of 1 GPa, which is considered to be a quantum critical point. Neither at 0 - 0.5 nor 2 GPa but only around this critical point in pressure, field-induced phases appear from 0.2 T through 10 T, where Rxy is almost constant and Rxx is very low. These phenomena are achieved when the magnetic field is applied along the least conducting axis. The behaviors are consistent with a kind of Quantum Hall Effect (QHE). The field-induce phase accompanied by the QHE might be the field-induced CDW (FICDW) similar to that of FISDW, observed in (TMTSF)2X salts. This paper presents the latest result of the Hall effects reviewing the history of the authors’ work on this material from preliminary to the latest ones.展开更多
Ferroelectric oxide films with a large field-induced polarization can be used in dielectric capacitors for charge or energy storage in microelectronic systems and hence have attracted intense research interest.A high ...Ferroelectric oxide films with a large field-induced polarization can be used in dielectric capacitors for charge or energy storage in microelectronic systems and hence have attracted intense research interest.A high processing temperature is usually required to produce a well-crystallized polar phase and hence a large polarization in the film,corresponding to a high charge or energy density.However,high processing temperature not only reduces the charge‒discharge efficiency by producing a sizable remnant polarization but is also incompatible with the integration process.In this study,we address this problem by creating a large field-induced polarization(~55.8μC/cm^(2))in BaTiO_(3)films sputter-deposited on Si at 200℃ via a buffer-layer technique.This large polarization led to a high energy density and efficiency(Wrec≈94.7 J/cm^(3),η≈78.2%@4 MV/cm).The thickness of LaNiO_(3)buffer layer was revealed to be the key factor determining the electric polarization(remnant and field-induced ones).A 50 nm LaNiO_(3)thickness,corresponding to the aforementioned polarization and energy storage performance,not only ensures proper crystallization in the BaTiO_(3)film,but also leads to an optimal combination of polycrystalline grains with a high dielectric constant.The latter accounts for the majority of the field-induced polarization.Our results revealed the key role of a buffer layer in tuning the microstructure of a low-temperature deposited ferroelectric oxide film.Furthermore,the excellent charge/energy storage performance of these 200℃-deposited BaTiO_(3)films has provided many opportunities for this simple dielectric in microelectronics.展开更多
CdSe quantum-dot(QD)film,as the core function layer,plays a key role in various optoelectronic devices.The thickness uniformity of QD films is one of the key factors to determine the overall photoelectric performance....CdSe quantum-dot(QD)film,as the core function layer,plays a key role in various optoelectronic devices.The thickness uniformity of QD films is one of the key factors to determine the overall photoelectric performance.Therefore,it is important to obtain the thickness distribution of large-area QD films.However,it is difficult for traditional methods to quickly get the information related to its thickness distribution without introducing additional damage.In this paper,a non-contact and non-destructive inspection method for in-situ detecting the thickness uniformity of CdSe QD film is proposed.The principle behind this in-situ inspection method is that the photoluminescence quenching phenomenon of the QD film would occur under a high electric field,and the degree of photoluminescence quenching is related to the thickness of the quantum dot films.Photoluminescence images of the same QD film without and with an electric field are recorded by a charge-coupled device camera,respectively.By transforming the brightness distribution of these two images,we can intuitively see the thickness information of the thin film array of QD.The proposed method provides a meaningful inspection for the manufacture of QD based lightemitting display.展开更多
Piezophotonics is a great interesting field of physics that has led to a number of important technologies,such as light source,smart sensors,and mechatronics.In this work,we reported Pr-doped(Bi_(0.5)Na_(0.5))TiO_(3)-...Piezophotonics is a great interesting field of physics that has led to a number of important technologies,such as light source,smart sensors,and mechatronics.In this work,we reported Pr-doped(Bi_(0.5)Na_(0.5))TiO_(3)-based lead-free ceramics with strong red photoluminescence emission and large strain response(d_(33)^(*)=460 pm/V,S=0.32%).The PL emission can be quenched by decreasing the intensity by 93%after electrical polarization(E=50 kV/cm).The local structure and electric field-induced structural changes were systematically investigated to reveal the significant distinction in photoluminescence properties caused by electrical polarization.The results indicated that polarization treatment eliminates the structural inhomogeneities and establishes a long-range ferroelectric tetragonal and rhombohedral distortion.The crystal structure transformed irreversibly from a non-ergodic to a normal ferroelectric state.PL quenching originated from the decreased distortion of octahedral due to the transition from a non-ergodic state to a highly ordered symmetrical structure.Meanwhile,the enlarged domain structure contributed to the photoluminescence quenching effect.Our findings demonstrate that an electric field can be a robust tool for adjusting the photoluminescence property and provide insights into the rela-tionship between the structure and PL properties of BNT-based ceramics under an external stimulus.展开更多
The interaction between complex magnetic structures and non-trivial band structures in ternary rare-earth GdCr_(6)Ge_(6) induces exotic and abundant electro-magnetic phenomena.In this work,we perform a systematical in...The interaction between complex magnetic structures and non-trivial band structures in ternary rare-earth GdCr_(6)Ge_(6) induces exotic and abundant electro-magnetic phenomena.In this work,we perform a systematical investigation on critical behaviors and magnetic properties of the single-crystal GdCr_(6)Ge_(6).The temperature,field,and angle dependence of magnetization unveils strong magnetic anisotropy along the c-axis and isotropic characteristic in the ab-plane.Critical exponentsβ=0.252(1),γ=0.905(9),δ=4.606(3)for H//ab,andβ=0.281(3),γ=0.991(8),δ=4.541(5)for H//c are obtained by the modified Arrott plot method(MAP)and critical isotherm(CI)analysis.The determined exponents for both directions are consistent with the theoretical prediction of a tricritical mean-field model.Based on detailed magnetization measurements and universality scaling,comprehensive magnetic phase diagrams of GdCr6Ge6for H//ab and H//c are constructed,which reveal that the external field induces a ferromagnetic(FM)transition for H//ab while a ferrimagnetic(FIM)one for H//c.Two tricritical points are determined for H//ab(11.2 K,266.3 Oe)and H//c(11.3 K,3.3 kOe)on the phase diagrams,respectively.The field-induced anisotropic magnetic configurations and multiple phases are clarified,where the moments of Gd and Cr form FM coupling for H//ab while FIM one for H//c via the interaction between Gd and Cr sublattices.展开更多
We report an interesting study of electric-field-induced transformation from a single domain ferroelectric state to the multiple domain ferroelectric state in a KTa_(1-x)Nb_(x)O_(3)(KTN) crystal. Experimental results ...We report an interesting study of electric-field-induced transformation from a single domain ferroelectric state to the multiple domain ferroelectric state in a KTa_(1-x)Nb_(x)O_(3)(KTN) crystal. Experimental results obtained using the confocalμ-Raman spectroscopy confirm the dynamic change of lattice structures induced by an external electric field.Furthermore, the dependence of relative permittivity on the applied voltage also indicates the transformation of ferroelectric states involving the processes of splintering, inversion, and re-formation of ferroelectric domains.展开更多
A novel coupled quantum well structure - quasi-symmetric coupled quantum well （QSCQW） is proposed. In the case of low applied electric field （F = 25 kV/cm） and low absorption loss （a ≈ 100 cm^-1）, a large field...A novel coupled quantum well structure - quasi-symmetric coupled quantum well （QSCQW） is proposed. In the case of low applied electric field （F = 25 kV/cm） and low absorption loss （a ≈ 100 cm^-1）, a large field-induced refractive index change （for TE mode, △n = 0.0106; for TM mode, △n = 0.0115） is obtained in QSCQW structure at operating wavelength λ = 1550 nm. The value is larger by over one to two order of magnitude compared to that in a rectangular quantum well （RQW） and about 50% larger than that of five-step asymmetric coupled quantum well （FACQW） structure under the above work conditions.展开更多
The multiple field-induced phase transition in 4 at.% La modified Pb(Zr,Sn,Ti)O 3 family with temperature from -40℃ to 45℃ in reported. Two electric field-induced transitions from a metastable antiferroelectric phas...The multiple field-induced phase transition in 4 at.% La modified Pb(Zr,Sn,Ti)O 3 family with temperature from -40℃ to 45℃ in reported. Two electric field-induced transitions from a metastable antiferroelectric phase to two ferroelectric phases are observed is polarization at the applied field of 4 MV/m. The critical field of phase transition between two ferroelectric phases is not larger than 2.5 MV/m, about ten to twenty percent of that ever found in PZT based ceramics. Lattice structure is shown to be orthorhombic by X-ray diffraction. Dielectric investigation reveals a relaxor-like ferroelectric behavior. Temperature-electric field phase diagram is also presented. An appreciate kind of materials is provided to investigate multiple field-induced phase transition with PZT-based ceramics.展开更多
Lead-free ferroelectric ceramics,0.67Bi_(1-x)Eu_(x)FeO_(3)-0.33BaTiO_(3)(BF-BT-xEu,x=0-0.02),were prepared via a solid-state reaction,The effect of Eu^(3+) doping on the microstructure,dielectric properties,ferroelect...Lead-free ferroelectric ceramics,0.67Bi_(1-x)Eu_(x)FeO_(3)-0.33BaTiO_(3)(BF-BT-xEu,x=0-0.02),were prepared via a solid-state reaction,The effect of Eu^(3+) doping on the microstructure,dielectric properties,ferroelectric properties,and electric-field-induced strain was investigated.The X-ray diffraction(XRD) results indicate the presence of a mixed phase of tetragonal and rhombohedral at the morphotropic phase boundary(MPB).Doping with an appropriate amount of Eu^(3+) reduces the Fe^(3+) content and decreases the leakage current in the binary system.A converse piezoelectric coefficient(d_(33)*) of 392 pm/V is obtained at BF-BT-0.003Eu under an electric field of 60 kV/cm at room temperature,which has a Curie temperature(T_(C)) of 414℃,The unipolar strain and d_(33)* of BF-BT-0.003Eu ceramics increase to 0.438%and 730 pm/V at 125℃ The field-induced strain response of the BF-BT-0.003Eu ceramics is greater than that of 0.67BF-0.33BT,mainly due to its optimal grain size,reduction of leakage current,and coexistence of ferroelectric-relaxation phases,BF-BT-0.003Eu ceramic is a lead-free candidate for high-temperature actuator applications.展开更多
Giant magnetic field induced strain （MFIS） up to 6.2% is achieved in the Ni50Mn27.5Ga22.5 single crystals with 5 M martensitic structure at room temperature. The switching magnetic field was about 2.4 kOe for the ma...Giant magnetic field induced strain （MFIS） up to 6.2% is achieved in the Ni50Mn27.5Ga22.5 single crystals with 5 M martensitic structure at room temperature. The switching magnetic field was about 2.4 kOe for the magnetostrain. A ‘magnetization jump＇ effect in the switching field applied along the initially hard direction confirms the occurrence of the large magnetostrain. The temperature dependence of the magnetostrain is investigated in lower temperature range. A linear decrease of the magnetostrain is observed with increasing temperature, but a strong decrease is monitored near the reverse martensitic transformation temperature.展开更多
Epitaxial Ni–Mn–Ga thin films have promising application potential in micro-electro-mechanical sensing and actuation systems. To date, large abrupt magnetization changes have been observed in some epitaxial Ni–Mn–...Epitaxial Ni–Mn–Ga thin films have promising application potential in micro-electro-mechanical sensing and actuation systems. To date, large abrupt magnetization changes have been observed in some epitaxial Ni–Mn–Ga thin films, but their origin-either from magnetically induced martensite variant reorientation(MIR) or magnetic domain evolution-has been discussed controversially. In the present work, we investigated the evolutions of the magnetic domain and microstructure of a typical epitaxial Ni–Mn–Ga thin film through wide-field magneto-optical Kerr-microscopy. It is demonstrated that the abrupt magnetization changes in the hysteresis loops should be attributed to the magnetic domain evolution instead of the MIR.展开更多
The pulsed magnetic field induced martensitic transformation with isothermal and athermal kinetics in Fe-2Ni-4Mn(wt-%)alloy has been studied by means of magnetization measurements,optical microscopy and thermodymical ...The pulsed magnetic field induced martensitic transformation with isothermal and athermal kinetics in Fe-2Ni-4Mn(wt-%)alloy has been studied by means of magnetization measurements,optical microscopy and thermodymical analyses.It is shown that there exits a critical magnetic intensity for induing martensitic transformation at a given temperature above Ms.The critical magnetic field increases linearly with increasing ΔT= T-M_S.The magnetic field strongly promotes the athermal martensitic transforamtion and restrains the isothermal one.The entropy change ΔS for athermal transformation at Ms is 4.13 J/mol· K.The effect of magnetic field on martensitic transformation in Fe-21Ni-4Mn alloy is main- ly due to Zeeman effect.Lath,plate and butterfly martensities were observed under magnetic field.展开更多
Gambling is a useful analog to thermodynamics. When all players use the same dice, loaded or not, on the average no one wins. In thermodynamic terms, when the system is homogeneous—an assumption made by Boltzmann in ...Gambling is a useful analog to thermodynamics. When all players use the same dice, loaded or not, on the average no one wins. In thermodynamic terms, when the system is homogeneous—an assumption made by Boltzmann in his H-Theorem—entropy never decreases. To reliably win, one must cheat, for example, use a loaded dice when everyone else uses a fair dice;in thermodynamics, one must use a heterogeneous statistical strategy. This can be implemented by combining within a single system, different statistics such as Maxwell-Boltzmann’s, Fermi-Dirac’s and Bose-Einstein’s. Heterogeneous statistical systems fall outside of Boltzmann’s assumption and therefore can bypass the second law. The Maxwell-Boltzmann statistics, the equivalent of an unbiased fair dice, requires a gas column to be isothermal. The Fermi-Dirac and Bose-Einstein statistics, the equivalent of a loaded biased dice, can generate spontaneous temperature gradients when a field is present. For example, a thermoelectric junction can produce a spontaneous temperature gradient, an experimentally documented phenomenon. A magnetic field parallel to, and an electric field perpendicular to a surface produce a spontaneous current along the surface, perpendicular to both fields (Reciprocal Hall Effect). Experimental data collected by several independent researchers is cited to support the theory.展开更多
Dielectric,hysteresis(P–E)loops and TSDC properties of transparent 85PZN–15BT ceramic over150–150℃ were investigated.The sample was found to exhibit a strong relaxor behavior and a relatively small remanent polar...Dielectric,hysteresis(P–E)loops and TSDC properties of transparent 85PZN–15BT ceramic over150–150℃ were investigated.The sample was found to exhibit a strong relaxor behavior and a relatively small remanent polarization.TSDC studies showed that there existed an electric field-dependent peak in the p versus T.Such interesting features were attributed to the electric field-induced transition and coexistence of polar nanoregion,long-range ordered polar region and nonpolarizable BZN-rich region.展开更多
基金Supported by the National Basic Research Program of China under Grant No 2011CBA00111the National Natural Science Foundation of China under Grant No U1332143
文摘The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr2 Se4 at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity experiments. With an increase in the magnetic field H, the antiferromagnetic transition temperature TN is observed to shift progressively toward lower temperatures. The corresponding high temperature cubic （Fd3m） to low temperature tetragonal （I41amd） structural transition is tuned simultaneously due to the inherent strong spin-lattice coupling. In the antiferromagnetic phase, an anomaly at Hc2 defined as a steep downward peak in the derivative of the M-H curve is dearly drawn. It is found that TN versus H and Hc2 versus T exhibit a consistent tendency, indicative of a field-induced tetragonal （I41amd） to cubic （Fd3m） structural transition. The transition is further substantiated by the field-dependent dielectric constant and thermal conductivity measurements. We modify the T-H phase diagram, highlighting the coexistence of the paramagnetic state and ferromagnetic clusters between 100K and TN.
文摘In the Temperature-Pressure phase diagram, the quasi-one-dimensional conductor, HMTSF-TCNQ, the ground state at ambient pressure is an insulator of charge density wave (CDW) below 30 K, while it shows a good metallic nature at higher temperature. The CDW insulating state is suppressed by a pressure of 1 GPa, which is considered to be a quantum critical point. Neither at 0 - 0.5 nor 2 GPa but only around this critical point in pressure, field-induced phases appear from 0.2 T through 10 T, where Rxy is almost constant and Rxx is very low. These phenomena are achieved when the magnetic field is applied along the least conducting axis. The behaviors are consistent with a kind of Quantum Hall Effect (QHE). The field-induce phase accompanied by the QHE might be the field-induced CDW (FICDW) similar to that of FISDW, observed in (TMTSF)2X salts. This paper presents the latest result of the Hall effects reviewing the history of the authors’ work on this material from preliminary to the latest ones.
基金supported by the Natural Science Foundation of Shandong Province(Nos.ZR2022ZD39,ZR2022QB138,ZR2020QE042,ZR2023QE138,ZR2022QB119,and ZR2022ME031)the National Natural Science Foundation of China(Nos.92463306 and 52002192)+4 种基金the Innovation Capacity Improvement Project of Small and Medium-sized Technologybased Enterprises of Shandong Province(No.2021TSGC1087)the Jinan City Science and Technology Bureau(No.2021GXRC055)the Science,Education and Industry Integration Pilot Projects of Qilu University of Technology(Shandong Academy of Sciences)(Nos.2022GH018,2023PX062,and 2023PX041)the Seed Funding for Top Talents at Qilu University of Technology(Shandong Academy of Sciences)the Excellent Teaching Team Training Plan Project of Qilu University of Technology,the Education Department of Hunan Province/Xiangtan University(No.KZ0807969).
文摘Ferroelectric oxide films with a large field-induced polarization can be used in dielectric capacitors for charge or energy storage in microelectronic systems and hence have attracted intense research interest.A high processing temperature is usually required to produce a well-crystallized polar phase and hence a large polarization in the film,corresponding to a high charge or energy density.However,high processing temperature not only reduces the charge‒discharge efficiency by producing a sizable remnant polarization but is also incompatible with the integration process.In this study,we address this problem by creating a large field-induced polarization(~55.8μC/cm^(2))in BaTiO_(3)films sputter-deposited on Si at 200℃ via a buffer-layer technique.This large polarization led to a high energy density and efficiency(Wrec≈94.7 J/cm^(3),η≈78.2%@4 MV/cm).The thickness of LaNiO_(3)buffer layer was revealed to be the key factor determining the electric polarization(remnant and field-induced ones).A 50 nm LaNiO_(3)thickness,corresponding to the aforementioned polarization and energy storage performance,not only ensures proper crystallization in the BaTiO_(3)film,but also leads to an optimal combination of polycrystalline grains with a high dielectric constant.The latter accounts for the majority of the field-induced polarization.Our results revealed the key role of a buffer layer in tuning the microstructure of a low-temperature deposited ferroelectric oxide film.Furthermore,the excellent charge/energy storage performance of these 200℃-deposited BaTiO_(3)films has provided many opportunities for this simple dielectric in microelectronics.
基金financially supported by the National Key Research and Development Program of China(2021YFB3600400)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China Project(2020ZZ113 and 2021ZZ130)。
文摘CdSe quantum-dot(QD)film,as the core function layer,plays a key role in various optoelectronic devices.The thickness uniformity of QD films is one of the key factors to determine the overall photoelectric performance.Therefore,it is important to obtain the thickness distribution of large-area QD films.However,it is difficult for traditional methods to quickly get the information related to its thickness distribution without introducing additional damage.In this paper,a non-contact and non-destructive inspection method for in-situ detecting the thickness uniformity of CdSe QD film is proposed.The principle behind this in-situ inspection method is that the photoluminescence quenching phenomenon of the QD film would occur under a high electric field,and the degree of photoluminescence quenching is related to the thickness of the quantum dot films.Photoluminescence images of the same QD film without and with an electric field are recorded by a charge-coupled device camera,respectively.By transforming the brightness distribution of these two images,we can intuitively see the thickness information of the thin film array of QD.The proposed method provides a meaningful inspection for the manufacture of QD based lightemitting display.
基金This work was supported by the Natural Science Foundation of Shandong Province of China(No.ZR2020ME031,ZR2020ME033,ZR2020QE043,ZR2020QE044)the Innovation Team of Higher Educational Science and Technology Program in Shandong Province(No.2019KJA025)Key Laboratory of Inorganic Functional Ma-terials and Devices,Chinese Academy of Sciences(Grant No.KLIFMD202008).
文摘Piezophotonics is a great interesting field of physics that has led to a number of important technologies,such as light source,smart sensors,and mechatronics.In this work,we reported Pr-doped(Bi_(0.5)Na_(0.5))TiO_(3)-based lead-free ceramics with strong red photoluminescence emission and large strain response(d_(33)^(*)=460 pm/V,S=0.32%).The PL emission can be quenched by decreasing the intensity by 93%after electrical polarization(E=50 kV/cm).The local structure and electric field-induced structural changes were systematically investigated to reveal the significant distinction in photoluminescence properties caused by electrical polarization.The results indicated that polarization treatment eliminates the structural inhomogeneities and establishes a long-range ferroelectric tetragonal and rhombohedral distortion.The crystal structure transformed irreversibly from a non-ergodic to a normal ferroelectric state.PL quenching originated from the decreased distortion of octahedral due to the transition from a non-ergodic state to a highly ordered symmetrical structure.Meanwhile,the enlarged domain structure contributed to the photoluminescence quenching effect.Our findings demonstrate that an electric field can be a robust tool for adjusting the photoluminescence property and provide insights into the rela-tionship between the structure and PL properties of BNT-based ceramics under an external stimulus.
基金supported by the National Natural Science Foundation of China(Grant Nos.12074386,11874358,U1432138,11974181,12204006,and 12250410238)the Collaborative Innovation Program of Hefei Science Center,CAS(Grant No.2021HSC-CIP006)+3 种基金the Alliance of International Science Organizations(Grant No.ANSO-VF-2022-03)the Key Project of Natural Scientific Research of Universities in Anhui Province(Grant No.K120462009)the Anhui Provincial Natural Science Foundation(Grant No.2108085QA21)supported by the High Magnetic Field Laboratory of Anhui Province。
文摘The interaction between complex magnetic structures and non-trivial band structures in ternary rare-earth GdCr_(6)Ge_(6) induces exotic and abundant electro-magnetic phenomena.In this work,we perform a systematical investigation on critical behaviors and magnetic properties of the single-crystal GdCr_(6)Ge_(6).The temperature,field,and angle dependence of magnetization unveils strong magnetic anisotropy along the c-axis and isotropic characteristic in the ab-plane.Critical exponentsβ=0.252(1),γ=0.905(9),δ=4.606(3)for H//ab,andβ=0.281(3),γ=0.991(8),δ=4.541(5)for H//c are obtained by the modified Arrott plot method(MAP)and critical isotherm(CI)analysis.The determined exponents for both directions are consistent with the theoretical prediction of a tricritical mean-field model.Based on detailed magnetization measurements and universality scaling,comprehensive magnetic phase diagrams of GdCr6Ge6for H//ab and H//c are constructed,which reveal that the external field induces a ferromagnetic(FM)transition for H//ab while a ferrimagnetic(FIM)one for H//c.Two tricritical points are determined for H//ab(11.2 K,266.3 Oe)and H//c(11.3 K,3.3 kOe)on the phase diagrams,respectively.The field-induced anisotropic magnetic configurations and multiple phases are clarified,where the moments of Gd and Cr form FM coupling for H//ab while FIM one for H//c via the interaction between Gd and Cr sublattices.
基金This work was supported by the Natural Science Foundation of Tianjin(No.19JCZDJC32700)the Fundamental Research Funds for the Central Universities。
文摘We report an interesting study of electric-field-induced transformation from a single domain ferroelectric state to the multiple domain ferroelectric state in a KTa_(1-x)Nb_(x)O_(3)(KTN) crystal. Experimental results obtained using the confocalμ-Raman spectroscopy confirm the dynamic change of lattice structures induced by an external electric field.Furthermore, the dependence of relative permittivity on the applied voltage also indicates the transformation of ferroelectric states involving the processes of splintering, inversion, and re-formation of ferroelectric domains.
基金This work was supported by the National NaturalScience Foundation of China under Grant No. 60277034,60436020.
文摘A novel coupled quantum well structure - quasi-symmetric coupled quantum well （QSCQW） is proposed. In the case of low applied electric field （F = 25 kV/cm） and low absorption loss （a ≈ 100 cm^-1）, a large field-induced refractive index change （for TE mode, △n = 0.0106; for TM mode, △n = 0.0115） is obtained in QSCQW structure at operating wavelength λ = 1550 nm. The value is larger by over one to two order of magnitude compared to that in a rectangular quantum well （RQW） and about 50% larger than that of five-step asymmetric coupled quantum well （FACQW） structure under the above work conditions.
文摘The multiple field-induced phase transition in 4 at.% La modified Pb(Zr,Sn,Ti)O 3 family with temperature from -40℃ to 45℃ in reported. Two electric field-induced transitions from a metastable antiferroelectric phase to two ferroelectric phases are observed is polarization at the applied field of 4 MV/m. The critical field of phase transition between two ferroelectric phases is not larger than 2.5 MV/m, about ten to twenty percent of that ever found in PZT based ceramics. Lattice structure is shown to be orthorhombic by X-ray diffraction. Dielectric investigation reveals a relaxor-like ferroelectric behavior. Temperature-electric field phase diagram is also presented. An appreciate kind of materials is provided to investigate multiple field-induced phase transition with PZT-based ceramics.
基金Project supported by the National Natural Science Foundation of China Youth Project (51702317)the Youth Project of the Natural Science Foundation of Jiangxi Provincial Science and Technology (20212BAB214019)the Program of Qingjiang Excellent Young Talents of Jiangxi University of Science and Technology (JXUSTQJYX2020004)。
文摘Lead-free ferroelectric ceramics,0.67Bi_(1-x)Eu_(x)FeO_(3)-0.33BaTiO_(3)(BF-BT-xEu,x=0-0.02),were prepared via a solid-state reaction,The effect of Eu^(3+) doping on the microstructure,dielectric properties,ferroelectric properties,and electric-field-induced strain was investigated.The X-ray diffraction(XRD) results indicate the presence of a mixed phase of tetragonal and rhombohedral at the morphotropic phase boundary(MPB).Doping with an appropriate amount of Eu^(3+) reduces the Fe^(3+) content and decreases the leakage current in the binary system.A converse piezoelectric coefficient(d_(33)*) of 392 pm/V is obtained at BF-BT-0.003Eu under an electric field of 60 kV/cm at room temperature,which has a Curie temperature(T_(C)) of 414℃,The unipolar strain and d_(33)* of BF-BT-0.003Eu ceramics increase to 0.438%and 730 pm/V at 125℃ The field-induced strain response of the BF-BT-0.003Eu ceramics is greater than that of 0.67BF-0.33BT,mainly due to its optimal grain size,reduction of leakage current,and coexistence of ferroelectric-relaxation phases,BF-BT-0.003Eu ceramic is a lead-free candidate for high-temperature actuator applications.
基金Supported by the National Natural Science Foundation of China under Grant No 50271002, and the New Century Programme for Excellent Talents of the Ministry of Education of China under Grant No 04-0165.
文摘Giant magnetic field induced strain （MFIS） up to 6.2% is achieved in the Ni50Mn27.5Ga22.5 single crystals with 5 M martensitic structure at room temperature. The switching magnetic field was about 2.4 kOe for the magnetostrain. A ‘magnetization jump＇ effect in the switching field applied along the initially hard direction confirms the occurrence of the large magnetostrain. The temperature dependence of the magnetostrain is investigated in lower temperature range. A linear decrease of the magnetostrain is observed with increasing temperature, but a strong decrease is monitored near the reverse martensitic transformation temperature.
基金supported by the National Natural Science Foundation of China (Grants Nos. 52071071)the Liaoning Revitalization Talents Program (Grant No. XLYC1802023)+1 种基金the Fundamental Research Funds for the Central Universities of China (Grant Nos. N2102006)the Program of Introducing Talents of Discipline Innovation to Universities 2.0 (the 111 Project of China 2.0, No. BP0719037)。
文摘Epitaxial Ni–Mn–Ga thin films have promising application potential in micro-electro-mechanical sensing and actuation systems. To date, large abrupt magnetization changes have been observed in some epitaxial Ni–Mn–Ga thin films, but their origin-either from magnetically induced martensite variant reorientation(MIR) or magnetic domain evolution-has been discussed controversially. In the present work, we investigated the evolutions of the magnetic domain and microstructure of a typical epitaxial Ni–Mn–Ga thin film through wide-field magneto-optical Kerr-microscopy. It is demonstrated that the abrupt magnetization changes in the hysteresis loops should be attributed to the magnetic domain evolution instead of the MIR.
文摘The pulsed magnetic field induced martensitic transformation with isothermal and athermal kinetics in Fe-2Ni-4Mn(wt-%)alloy has been studied by means of magnetization measurements,optical microscopy and thermodymical analyses.It is shown that there exits a critical magnetic intensity for induing martensitic transformation at a given temperature above Ms.The critical magnetic field increases linearly with increasing ΔT= T-M_S.The magnetic field strongly promotes the athermal martensitic transforamtion and restrains the isothermal one.The entropy change ΔS for athermal transformation at Ms is 4.13 J/mol· K.The effect of magnetic field on martensitic transformation in Fe-21Ni-4Mn alloy is main- ly due to Zeeman effect.Lath,plate and butterfly martensities were observed under magnetic field.
文摘Gambling is a useful analog to thermodynamics. When all players use the same dice, loaded or not, on the average no one wins. In thermodynamic terms, when the system is homogeneous—an assumption made by Boltzmann in his H-Theorem—entropy never decreases. To reliably win, one must cheat, for example, use a loaded dice when everyone else uses a fair dice;in thermodynamics, one must use a heterogeneous statistical strategy. This can be implemented by combining within a single system, different statistics such as Maxwell-Boltzmann’s, Fermi-Dirac’s and Bose-Einstein’s. Heterogeneous statistical systems fall outside of Boltzmann’s assumption and therefore can bypass the second law. The Maxwell-Boltzmann statistics, the equivalent of an unbiased fair dice, requires a gas column to be isothermal. The Fermi-Dirac and Bose-Einstein statistics, the equivalent of a loaded biased dice, can generate spontaneous temperature gradients when a field is present. For example, a thermoelectric junction can produce a spontaneous temperature gradient, an experimentally documented phenomenon. A magnetic field parallel to, and an electric field perpendicular to a surface produce a spontaneous current along the surface, perpendicular to both fields (Reciprocal Hall Effect). Experimental data collected by several independent researchers is cited to support the theory.
基金financially supported by the National Key R&D Program on Nano Science&Technology of the MOST(2022YFA1203600)the National Natural Science Foundation of China(U2032161,21925110,22321001,21890750)+3 种基金CAS Project for Young Scientists in Basic Research(YSBR-070)USTC Research Funds of the Double First-Class Initiative(YD2060002004)the Youth Innovation Promotion Association CAS(2018500)the Key R&D Program of Shandong Province(2021CXGC010302)。
基金supported by the National Key Project for Basic Research of China(2009CB623305)the National Nature Science Foundation of China(Nos.61137004,51107140,and 61275181)the External Cooperation Program of the Chinese Academy of Sciences(No.GJHZ1042).
文摘Dielectric,hysteresis(P–E)loops and TSDC properties of transparent 85PZN–15BT ceramic over150–150℃ were investigated.The sample was found to exhibit a strong relaxor behavior and a relatively small remanent polarization.TSDC studies showed that there existed an electric field-dependent peak in the p versus T.Such interesting features were attributed to the electric field-induced transition and coexistence of polar nanoregion,long-range ordered polar region and nonpolarizable BZN-rich region.
