Long-range magnetic order appears on a side decorated Heisenberg spin nanoribbon at nonzero temperature,although no spontaneous magnetization exists in a one-or two-dimensional isotropic Heisenberg model at any nonzer...Long-range magnetic order appears on a side decorated Heisenberg spin nanoribbon at nonzero temperature,although no spontaneous magnetization exists in a one-or two-dimensional isotropic Heisenberg model at any nonzero temperature according to the Mermin-Wagner theorem.By use of the spin Green's function method,we calculated the magnetizations of Heisenberg nanoribbons decorated by side spins with single-ion anisotropy and found that the system exhibits a nonzero transition temperature,whether the decorated edge spins of the system link together or separate from each other.When the width of the nanoribbon achieves infinite limit,the transition temperatures of the system tend to the same finite constant eventually whether one edge or both edges are decorated by side spins in the nanoribbon.The results reveal that the magnetism of a low-dimensional spin system is different from that of a threedimensional spin system.When the single-ion anisotropy of edge spins in a Heisenberg spin nanoribbon can be modulated by an electric field experimentally,various useful long-range magnetic orders of the system can be obtained.This work can provide a detailed theoretical basis for designing and fabricating next-generation low-dimensional magnetic random-access memory.展开更多
A Monte Carlo simulated-annealing algorithm was used to study the magnetic state in an in-plane helimagnet layer on triangular lattice that exchange couples to an underlayer with strong out-of-plane anisotropy.In the ...A Monte Carlo simulated-annealing algorithm was used to study the magnetic state in an in-plane helimagnet layer on triangular lattice that exchange couples to an underlayer with strong out-of-plane anisotropy.In the single helimagnet layer with in-plane anisotropy(K),the formation of labyrinth-like domains with local spin spirals,instead of parallel stripes,is favored,and these domains rapidly transform into dense skyrmion crystals with increasing interfacial exchange coupling(J'),equivalent to a virtual magnetic field,and finally evolve to an out-of-plane uniform state at large enough J'.Moreover,with increasing K,the skyrmion crystal state can vary from regular 6-nearest-neighboring circular skyrmion arrangement to irregular squeezed skyrmions with less than 6 nearest neighbors when the in-plane anisotropy energy is higher than the interfacial exchange energy as the skyrmion number is maximized.Finally,we demonstrated that the antiferromagnetic underlayer cannot induce skyrmions while the chirality inversion can be achieved on top of an out-of-plane magnetization underlayer with 180°domain walls,supporting the experimental findings in FeGe thin film.This compelling advantage offers a fertile playground for exploring emergent phenomena that arise from interfacing magnetic skyrmions with additional functionalities.展开更多
文摘Long-range magnetic order appears on a side decorated Heisenberg spin nanoribbon at nonzero temperature,although no spontaneous magnetization exists in a one-or two-dimensional isotropic Heisenberg model at any nonzero temperature according to the Mermin-Wagner theorem.By use of the spin Green's function method,we calculated the magnetizations of Heisenberg nanoribbons decorated by side spins with single-ion anisotropy and found that the system exhibits a nonzero transition temperature,whether the decorated edge spins of the system link together or separate from each other.When the width of the nanoribbon achieves infinite limit,the transition temperatures of the system tend to the same finite constant eventually whether one edge or both edges are decorated by side spins in the nanoribbon.The results reveal that the magnetism of a low-dimensional spin system is different from that of a threedimensional spin system.When the single-ion anisotropy of edge spins in a Heisenberg spin nanoribbon can be modulated by an electric field experimentally,various useful long-range magnetic orders of the system can be obtained.This work can provide a detailed theoretical basis for designing and fabricating next-generation low-dimensional magnetic random-access memory.
基金The authors express their thanks to Dr.Gong Chen helping with this work.This work was 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)the Fundamental Research Funds for Central Universities(No.N182410008-1)。
文摘A Monte Carlo simulated-annealing algorithm was used to study the magnetic state in an in-plane helimagnet layer on triangular lattice that exchange couples to an underlayer with strong out-of-plane anisotropy.In the single helimagnet layer with in-plane anisotropy(K),the formation of labyrinth-like domains with local spin spirals,instead of parallel stripes,is favored,and these domains rapidly transform into dense skyrmion crystals with increasing interfacial exchange coupling(J'),equivalent to a virtual magnetic field,and finally evolve to an out-of-plane uniform state at large enough J'.Moreover,with increasing K,the skyrmion crystal state can vary from regular 6-nearest-neighboring circular skyrmion arrangement to irregular squeezed skyrmions with less than 6 nearest neighbors when the in-plane anisotropy energy is higher than the interfacial exchange energy as the skyrmion number is maximized.Finally,we demonstrated that the antiferromagnetic underlayer cannot induce skyrmions while the chirality inversion can be achieved on top of an out-of-plane magnetization underlayer with 180°domain walls,supporting the experimental findings in FeGe thin film.This compelling advantage offers a fertile playground for exploring emergent phenomena that arise from interfacing magnetic skyrmions with additional functionalities.
