We report a numerical study on the role of longrange dipolar interaction played on the creation and stabilization of skyrmion-(non)crystal structure in chiral ferromagnetic thin films without any anisotropies,based on...We report a numerical study on the role of longrange dipolar interaction played on the creation and stabilization of skyrmion-(non)crystal structure in chiral ferromagnetic thin films without any anisotropies,based on a Monte-Carlo simulation method.With the increase of external magnetic field,the microscopic spin configuration is transformed from a spin-spiral stripe or labyrinth structure,depending on the strength of dipolar interaction,into a skyrmion-(non)crystal structure,and then into a skyrmiongas structure,and finally into a ferromagnetic state.Interestingly,with the increase of dipolar interaction,the skyrmion-crystal structure evolves from a triangular arrangement into a square arrangement with the change of skyrmion shape from circle to square.For larger dipolar interactions,the skyrmion-crystal structure loses the regular arrangements and the skyrmions,remaining topological,exhibit different shapes and sizes and squeeze with each other,whose distributions are analogous to a non-crystal structure.Therefore,different skyrmion-(non)crystal structures are stabilized in different ranges of dipolar interactions,which further promotes the applications of skyrmions as non-volatile information carriers.展开更多
Tumor-targeted magnetic hyperthermia has recently attracted much attention.Magnetic nanoparticles(NPs) are heat mediator nanoprobes in magnetic hyperthermia for cancer treatment.In this paper,single cubic spinel struc...Tumor-targeted magnetic hyperthermia has recently attracted much attention.Magnetic nanoparticles(NPs) are heat mediator nanoprobes in magnetic hyperthermia for cancer treatment.In this paper,single cubic spinel structural Zn_(0.3)Fe_(2.7)O_(4) magnetic NPs with sizes of 14 nm-20 nm were synthesized,followed by coating with SiO_(2) shell.The SLP value of Zn_(0.3)Fe_(2.7)O_(4)/SiO_(2) NPs below 20 nm changes non-monotonically with the concentration of solution under the alternating current(AC) magnetic field of 430 kHz and 27 kA/m.SLP values of all Zn_(0.3)Fe_(2.7)O_(4)/SiO_(2) NPs appear a peak value with change of solution concentration.The solution concentrations with optimal SLP value decrease with increasing magnetic core size.This work can give guidance to the better prediction and control of the magnetic hyperthermia performance of materials in clinical applications.展开更多
We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the gro...We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the growth process and are able to reproduce the experimental patterns. The energy of electric dipole interaction is calculated and determined to be the driving force for the pattern formation and evolution. Based on these results, single crystalline films are obtained by enhancing the electric dipole interaction while limiting effects of other growth parameters.展开更多
SmCo/FeCo/SmCo trilayer was deposited with two different thickness configurations for soft phase (FeCo);50 nm/10 nm/50 nm and 50 nm/25 nm/50 nm were deposited on Si (111) substrate and Ta (50 nm) seed layer by RF magn...SmCo/FeCo/SmCo trilayer was deposited with two different thickness configurations for soft phase (FeCo);50 nm/10 nm/50 nm and 50 nm/25 nm/50 nm were deposited on Si (111) substrate and Ta (50 nm) seed layer by RF magnetron sputtering in a pressure, p, of 30 - 35 m Torr. After deposition the films were annealed under Ar atmosphere at temperature T equal to 923 and 973 for different times followed by quenching in water. X-ray diffraction patterns were obtained to identified phase presents and calculate average crystallite size. To study the effect of configuration thickness in soft phases, DC magnetic measurements were carried out;the measurements were done in the temperature interval of 300 - 50 K. Hysteresis loops collected at low temperatures exposed an increment in coercivity with the decrease of T and at same time, presented a “knee” in the second quadrant of the demagnetization curve, which suggests that the inter-layer exchange coupling becomes less effective, being more evident for sample with 50 nm/25 nm/50 nm thickness. Moreover, δM (H) plots were calculated from magnetic measurements at three different temperatures, T, equal to 300, 150 and 50 K, which corroborates that the dipolar interactions became stronger when thickness of soft phases increases. Finally, the thickness effect is attributed to the SmCo5 phase magnetocrystalline anisotropy constant, which is responsible for the exchange coupling length.展开更多
When a Bose-Einstein condensate is set to rotate, superfluid vortices will be formed, which finally condense into a vortex lattice as the rotation frequency further increases. We show that the dipole-dipole interactio...When a Bose-Einstein condensate is set to rotate, superfluid vortices will be formed, which finally condense into a vortex lattice as the rotation frequency further increases. We show that the dipole-dipole interactions renormalize the short-range interaction strength and result in a distinction between interactions of parallel-polarized atoms and interactions of antiparallel-polarized atoms. This effect may lead to a spontaneous breakdown of the rapidly rotating Bose condensate into a novel anti-ferromagnetic-like vortex lattice. The upward-polarized Bose condensate forms a vortex lattice, which is staggered against a downward-polarized vortex lattice. A phase diagram related to the coupling strength is obtained.展开更多
A series of “H-shaped” organic dimers （azobenzene derivatives） exhibit linear absorption red shift compared with their corresponding monomers experimentally. Dipolar interaction model is not appropriate for the az...A series of “H-shaped” organic dimers （azobenzene derivatives） exhibit linear absorption red shift compared with their corresponding monomers experimentally. Dipolar interaction model is not appropriate for the azobenzene derivatives due to the small distance between two “D-π-A” chains. Energy transfer model is suggested for explanation of the absorption red shift. Two necessary conditions for energy transfer were verified. In addition, bi-exponential florescence-delay behavior of the dimer as well as Bella＇s quantum chemistry calculation shows evidence of energy transfer.展开更多
Magnetically anisotropic nanoparticle monolayer films are of great interest for the development of ap-plications such as high-density data storage,sensors.However,the formation of large-scale magnetically anisotropic ...Magnetically anisotropic nanoparticle monolayer films are of great interest for the development of ap-plications such as high-density data storage,sensors.However,the formation of large-scale magnetically anisotropic monolayer film is a challenging task.Here,we provide a new way to fabricate large-scale area of Fe_(3)O_(4) nanoparticle monolayer films by vacuum deposition technique(matrix-assisted pulsed laser evaporation,MAPLE).During the deposition process,only interactions between nanoparticles influence nanoparticle self-assembly behaviors.A strong magnetic anisotropy,characterized by in-plane and out-of-plane coercivity and saturation field obtained by DCM(dynamic cantilever magnetometry),was obtained both in cubic and spherical Fe_(3)O_(4) nanoparticle monolayer films.The inter-particle dipolar interaction but not crystal anisotropy is responsible for this effective magnetic anisotropy,which has been proved by Monte-Carlo simulations.展开更多
Many sandwich-type lanthanide complexes show extremely high energy barriers(Ueff)for the reversal of magnetization and high blocking temperatures,being the star molecules in the research area of single-molecule magnet...Many sandwich-type lanthanide complexes show extremely high energy barriers(Ueff)for the reversal of magnetization and high blocking temperatures,being the star molecules in the research area of single-molecule magnets.Herein,the preparation,structural determination,and magnetic property studies of two ansa-bridged Er-COT(COT=cyclooctatetraenyl dianion)complexes[KDME_(2)][Er((η^(8)-COT-Si^(Me2))_(2)O)](1)and[KDME_(2)][Er((η^(8)-COT-Si^(iPr2))_(2)O)]K[Er((η^(8)-COT-Si^(iPr2))_(2)O)](2)were reported.The Er(Ⅲ)ions in both complexes are sandwiched by two COT rings which are ansa-bridged by a[Si-O-Si]group.Magnetic studies reveal both complexes display slow magnetic relaxations with comparable energy barriers(228(5)K for 1,and 196(4)K for 2)and blocking temperatures(10.5 K for both complexes).The difference in the relaxation times(τ)for the two complexes was studied in details:different molecular vibrations induced by the substituents are the main reason forτfor 1 being about 10 times longer than for 2 at the same temperature above 10 K,while the quantum tunnelling of magnetization relaxation time(τQTM)for 2 is about 10 times longer than for 1 below 8 K,probably owing to the different dipolar interactions.Further rearrangement of molecular network with such ansa-bridged SMMs is promising to design molecular magnetic materials with enhanced properties or new properties.展开更多
基金financially supported by the National Natural Science Foundation of China(No.11774045)the Joint Research Fund Liaoning-Shenyang National Laboratory for Materials Science(No.20180510008)。
文摘We report a numerical study on the role of longrange dipolar interaction played on the creation and stabilization of skyrmion-(non)crystal structure in chiral ferromagnetic thin films without any anisotropies,based on a Monte-Carlo simulation method.With the increase of external magnetic field,the microscopic spin configuration is transformed from a spin-spiral stripe or labyrinth structure,depending on the strength of dipolar interaction,into a skyrmion-(non)crystal structure,and then into a skyrmiongas structure,and finally into a ferromagnetic state.Interestingly,with the increase of dipolar interaction,the skyrmion-crystal structure evolves from a triangular arrangement into a square arrangement with the change of skyrmion shape from circle to square.For larger dipolar interactions,the skyrmion-crystal structure loses the regular arrangements and the skyrmions,remaining topological,exhibit different shapes and sizes and squeeze with each other,whose distributions are analogous to a non-crystal structure.Therefore,different skyrmion-(non)crystal structures are stabilized in different ranges of dipolar interactions,which further promotes the applications of skyrmions as non-volatile information carriers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51771124,51571146,and 51701130)。
文摘Tumor-targeted magnetic hyperthermia has recently attracted much attention.Magnetic nanoparticles(NPs) are heat mediator nanoprobes in magnetic hyperthermia for cancer treatment.In this paper,single cubic spinel structural Zn_(0.3)Fe_(2.7)O_(4) magnetic NPs with sizes of 14 nm-20 nm were synthesized,followed by coating with SiO_(2) shell.The SLP value of Zn_(0.3)Fe_(2.7)O_(4)/SiO_(2) NPs below 20 nm changes non-monotonically with the concentration of solution under the alternating current(AC) magnetic field of 430 kHz and 27 kA/m.SLP values of all Zn_(0.3)Fe_(2.7)O_(4)/SiO_(2) NPs appear a peak value with change of solution concentration.The solution concentrations with optimal SLP value decrease with increasing magnetic core size.This work can give guidance to the better prediction and control of the magnetic hyperthermia performance of materials in clinical applications.
基金Project supported by the National Natural Science Foundation of China (Grant No.10774176)the National Basic Research Program of China (Grant No.2006CB806202)
文摘We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the growth process and are able to reproduce the experimental patterns. The energy of electric dipole interaction is calculated and determined to be the driving force for the pattern formation and evolution. Based on these results, single crystalline films are obtained by enhancing the electric dipole interaction while limiting effects of other growth parameters.
文摘SmCo/FeCo/SmCo trilayer was deposited with two different thickness configurations for soft phase (FeCo);50 nm/10 nm/50 nm and 50 nm/25 nm/50 nm were deposited on Si (111) substrate and Ta (50 nm) seed layer by RF magnetron sputtering in a pressure, p, of 30 - 35 m Torr. After deposition the films were annealed under Ar atmosphere at temperature T equal to 923 and 973 for different times followed by quenching in water. X-ray diffraction patterns were obtained to identified phase presents and calculate average crystallite size. To study the effect of configuration thickness in soft phases, DC magnetic measurements were carried out;the measurements were done in the temperature interval of 300 - 50 K. Hysteresis loops collected at low temperatures exposed an increment in coercivity with the decrease of T and at same time, presented a “knee” in the second quadrant of the demagnetization curve, which suggests that the inter-layer exchange coupling becomes less effective, being more evident for sample with 50 nm/25 nm/50 nm thickness. Moreover, δM (H) plots were calculated from magnetic measurements at three different temperatures, T, equal to 300, 150 and 50 K, which corroborates that the dipolar interactions became stronger when thickness of soft phases increases. Finally, the thickness effect is attributed to the SmCo5 phase magnetocrystalline anisotropy constant, which is responsible for the exchange coupling length.
基金The project supported by National Natural Science Foundation of China under Grant No. 10574012
文摘When a Bose-Einstein condensate is set to rotate, superfluid vortices will be formed, which finally condense into a vortex lattice as the rotation frequency further increases. We show that the dipole-dipole interactions renormalize the short-range interaction strength and result in a distinction between interactions of parallel-polarized atoms and interactions of antiparallel-polarized atoms. This effect may lead to a spontaneous breakdown of the rapidly rotating Bose condensate into a novel anti-ferromagnetic-like vortex lattice. The upward-polarized Bose condensate forms a vortex lattice, which is staggered against a downward-polarized vortex lattice. A phase diagram related to the coupling strength is obtained.
文摘A series of “H-shaped” organic dimers （azobenzene derivatives） exhibit linear absorption red shift compared with their corresponding monomers experimentally. Dipolar interaction model is not appropriate for the azobenzene derivatives due to the small distance between two “D-π-A” chains. Energy transfer model is suggested for explanation of the absorption red shift. Two necessary conditions for energy transfer were verified. In addition, bi-exponential florescence-delay behavior of the dimer as well as Bella＇s quantum chemistry calculation shows evidence of energy transfer.
基金financially supported by the National Natural Science Foundation of China (Nos.51771219,51771220 and 52171184)the Zhejiang Provincial Natural Science Foundation of China (No.LD19E010001)+2 种基金the Joint Research Fund Liaoning-Shenyang National Laboratory for Materials Science (No.20180510008)the National Key Research and Development Program of China (No.2017YFA0303201)the Major Program of Development Foundation of Hefei Center for Physical Science and Technology (No.2017FXZY003)。
文摘Magnetically anisotropic nanoparticle monolayer films are of great interest for the development of ap-plications such as high-density data storage,sensors.However,the formation of large-scale magnetically anisotropic monolayer film is a challenging task.Here,we provide a new way to fabricate large-scale area of Fe_(3)O_(4) nanoparticle monolayer films by vacuum deposition technique(matrix-assisted pulsed laser evaporation,MAPLE).During the deposition process,only interactions between nanoparticles influence nanoparticle self-assembly behaviors.A strong magnetic anisotropy,characterized by in-plane and out-of-plane coercivity and saturation field obtained by DCM(dynamic cantilever magnetometry),was obtained both in cubic and spherical Fe_(3)O_(4) nanoparticle monolayer films.The inter-particle dipolar interaction but not crystal anisotropy is responsible for this effective magnetic anisotropy,which has been proved by Monte-Carlo simulations.
基金supported by the National Natural Science Foundation of China(92261203,22101116,and 21971106)Key Laboratory of Rare Earth Chemistry of Guangdong Higher Education Institutes(2022KSYS006)+1 种基金the Stable Support Plan Program of Shenzhen Natural Science Fund(20200925161141006)Shenzhen Fundamental Research Program(JCYJ20220530115001002 and JCYJ20220818100417037).
文摘Many sandwich-type lanthanide complexes show extremely high energy barriers(Ueff)for the reversal of magnetization and high blocking temperatures,being the star molecules in the research area of single-molecule magnets.Herein,the preparation,structural determination,and magnetic property studies of two ansa-bridged Er-COT(COT=cyclooctatetraenyl dianion)complexes[KDME_(2)][Er((η^(8)-COT-Si^(Me2))_(2)O)](1)and[KDME_(2)][Er((η^(8)-COT-Si^(iPr2))_(2)O)]K[Er((η^(8)-COT-Si^(iPr2))_(2)O)](2)were reported.The Er(Ⅲ)ions in both complexes are sandwiched by two COT rings which are ansa-bridged by a[Si-O-Si]group.Magnetic studies reveal both complexes display slow magnetic relaxations with comparable energy barriers(228(5)K for 1,and 196(4)K for 2)and blocking temperatures(10.5 K for both complexes).The difference in the relaxation times(τ)for the two complexes was studied in details:different molecular vibrations induced by the substituents are the main reason forτfor 1 being about 10 times longer than for 2 at the same temperature above 10 K,while the quantum tunnelling of magnetization relaxation time(τQTM)for 2 is about 10 times longer than for 1 below 8 K,probably owing to the different dipolar interactions.Further rearrangement of molecular network with such ansa-bridged SMMs is promising to design molecular magnetic materials with enhanced properties or new properties.
