Interfacial magnetism in functional oxide heterostructures not only exhibits intriguing physical phenomena but also implies great potential for device applications.In these systems,interfacial structural and electroni...Interfacial magnetism in functional oxide heterostructures not only exhibits intriguing physical phenomena but also implies great potential for device applications.In these systems,interfacial structural and electronic reconstructions are essential for improving the stability and tunability of the magnetic properties.In this work,we constructed ultra-thinLa_(0.67)Ca_(0.33)MnO_(3)/SrRuO_(3)(SRO)layers into superlattices,which exhibited a robust ferromagnetic phase.The high Curie temperature(TC)reaches 291 K,more than 30 K higher than that of bulk LCMO.We found that the LCMO/SRO superlattices consisted of atomically-sharp and asymmetric heterointerfaces.Such a unique interface structure can trigger a sizable charge transfer as well as a ferroelectric-like polar distortion.These two interfacial effects cooperatively stabilized the high-T_(C)ferromagnetic phase.Our results could pave a promising approach towards effective control of interfacial magnetism and new designs of oxide-based spintronic devices.展开更多
The effect of electron itineracy on the magnetism of S＝1/2 ferromagnetic Ising model is investigated by introducing a hopping term. The electron Green's function method is used to deal with this Hamiltonian. Here...The effect of electron itineracy on the magnetism of S＝1/2 ferromagnetic Ising model is investigated by introducing a hopping term. The electron Green's function method is used to deal with this Hamiltonian. Here emphasis is made on that the magnetization is caused by the difference between the filling of spin-up and spin-down electrons.This concept is in accordance with that of band structure theory. In the zero band width limit, our results are the same as obtained by spin Green's function method. However, our method achieves more detailed physical information. The spontaneous magnetization, Curie temperature, total energy, and specific heat are calculated and investigated in detail by the densities of states. Hopping term depresses the Curie temperature but remains the order-disorder transformation still to be second order transition. Above the transition point, the energy band is the same as that of tight binding system because exchange interaction has no effect anymore. While under the transition point, the energy band splits into two subbands due to exchange interaction.展开更多
The Heisenberg-Kitaev(HK)model on various lattices has attracted a lot of attention because it may lead to exotic states such as quantum spin liquid and topological orders.The rare-earth-based kagome lattice(KL)compou...The Heisenberg-Kitaev(HK)model on various lattices has attracted a lot of attention because it may lead to exotic states such as quantum spin liquid and topological orders.The rare-earth-based kagome lattice(KL)compounds Mg_(2)RE_(3)Sb_(3)O_(14)(RE=Gd,Er)and(RE=Nd)have q=0,120°order and canted ferromagnetic(CFM)order,respectively.Interestingly,the HK model on the KL has the same ground state long-range orders.In the theoretical phase diagram,the CFM phase resides in a continuous parameter region and there is no phase change across special parameter points,such as the Kitaev ferromagnetic(KFM)point,the ferromagnetic(FM)point and its dual FM point.However,a ground state property cannot distinguish a system with or without topological nontrivial excitations and related phase transitions.Here,we study the topological magnon excitations and related thermal Hall conductivity in the HK model on the KL with CFM order.The CFM phase can be divided into two regions related by the Klein duality,with the self dual KFM point as their boundary.We find that the scalar spin chirality,which is intrinsic in the CFM order,changes sign across the KFM point.This leads to the opposite Chem numbers of corresponding magnon bands in the two regions,and also the sign change of the magnon thermal Hall conductivity.展开更多
Precessing ball solitons (PBS) in a ferromagnet during the first order phase transition induced by a magnetic field directed along the axis of anisotropy, while the additional action of high-frequency field perpendicu...Precessing ball solitons (PBS) in a ferromagnet during the first order phase transition induced by a magnetic field directed along the axis of anisotropy, while the additional action of high-frequency field perpendicular to the main magnetic field, are analyzed. It is shown that the spatial motion of solitons, associated with thermal fluctuations in the crystal, does not destroy the equilibrium of self-organized PBS.展开更多
Precessing ball solitons (PBS) in a ferromagnet during the first order phase transition is induced by a magnetic field directed along the axis of anisotropy, while the action of the periodic field perpendicular to the...Precessing ball solitons (PBS) in a ferromagnet during the first order phase transition is induced by a magnetic field directed along the axis of anisotropy, while the action of the periodic field perpendicular to the main magnetic field has been analyzed. Under these conditions, the characteristics of arising equilibrium PBS are uniquely determined by the frequency of the periodic field, but the solitons with other frequencies are impossible. For such structure, the entropy increase connected with dissipation is compensated by the decrease of the entropy due to the external periodic field. It is shown that the equilibrium PBS are essentially the “self-organizing systems” that can arise spotaneously in a metastable state of ferromagnet.展开更多
基金This work has supported by the National Basic Research Program of China(Nos.2016YFA0401003,2017YFA0403502,and 2020YFA0309100)the National Natural Science Foundation of China(Nos.11974326,12074365,11804342,U2032218,and 51872278)+2 种基金the Fundamental Research Funds for the Central Universities(Nos.WK2030000035 and WK2340000102)Hefei Science Center CAS.L.S.and K.H.were supported by the Austrian Science Fund(FWF)through Projects Nos.P30997 and P32044Calculations have been done on the Vienna Scientific Clusters(VSC).
文摘Interfacial magnetism in functional oxide heterostructures not only exhibits intriguing physical phenomena but also implies great potential for device applications.In these systems,interfacial structural and electronic reconstructions are essential for improving the stability and tunability of the magnetic properties.In this work,we constructed ultra-thinLa_(0.67)Ca_(0.33)MnO_(3)/SrRuO_(3)(SRO)layers into superlattices,which exhibited a robust ferromagnetic phase.The high Curie temperature(TC)reaches 291 K,more than 30 K higher than that of bulk LCMO.We found that the LCMO/SRO superlattices consisted of atomically-sharp and asymmetric heterointerfaces.Such a unique interface structure can trigger a sizable charge transfer as well as a ferroelectric-like polar distortion.These two interfacial effects cooperatively stabilized the high-T_(C)ferromagnetic phase.Our results could pave a promising approach towards effective control of interfacial magnetism and new designs of oxide-based spintronic devices.
文摘The effect of electron itineracy on the magnetism of S＝1/2 ferromagnetic Ising model is investigated by introducing a hopping term. The electron Green's function method is used to deal with this Hamiltonian. Here emphasis is made on that the magnetization is caused by the difference between the filling of spin-up and spin-down electrons.This concept is in accordance with that of band structure theory. In the zero band width limit, our results are the same as obtained by spin Green's function method. However, our method achieves more detailed physical information. The spontaneous magnetization, Curie temperature, total energy, and specific heat are calculated and investigated in detail by the densities of states. Hopping term depresses the Curie temperature but remains the order-disorder transformation still to be second order transition. Above the transition point, the energy band is the same as that of tight binding system because exchange interaction has no effect anymore. While under the transition point, the energy band splits into two subbands due to exchange interaction.
基金supported by the National Natural Science Foundation of China(Grant NO.12104407)the Natural Science Foundation of Zhejiang Province(Grant NO.LQ20A040004)
文摘The Heisenberg-Kitaev(HK)model on various lattices has attracted a lot of attention because it may lead to exotic states such as quantum spin liquid and topological orders.The rare-earth-based kagome lattice(KL)compounds Mg_(2)RE_(3)Sb_(3)O_(14)(RE=Gd,Er)and(RE=Nd)have q=0,120°order and canted ferromagnetic(CFM)order,respectively.Interestingly,the HK model on the KL has the same ground state long-range orders.In the theoretical phase diagram,the CFM phase resides in a continuous parameter region and there is no phase change across special parameter points,such as the Kitaev ferromagnetic(KFM)point,the ferromagnetic(FM)point and its dual FM point.However,a ground state property cannot distinguish a system with or without topological nontrivial excitations and related phase transitions.Here,we study the topological magnon excitations and related thermal Hall conductivity in the HK model on the KL with CFM order.The CFM phase can be divided into two regions related by the Klein duality,with the self dual KFM point as their boundary.We find that the scalar spin chirality,which is intrinsic in the CFM order,changes sign across the KFM point.This leads to the opposite Chem numbers of corresponding magnon bands in the two regions,and also the sign change of the magnon thermal Hall conductivity.
文摘铁磁共振测试是自旋电子学研究的重要手段,为实现简单高效的FMR测试,基于瑞士苏黎世仪器500k MFLI锁相放大器,搭建了微扰型宽频带共面波导式铁磁共振测试系统,并对坡莫合金等材料进行了测试.为了得到材料的真实性质,对影响实验结果的参量进行优化,在深入讨论了这些参量对实验结果的影响及其物理和数学机制后,得到准确铁磁共振测试结果的实验条件为:电磁铁定点增加模式下,锁相放大器的时间常量为100 ms,滤波阶数在2阶以上,微扰线圈驱动信号振幅为1~2 V,频率为33~200 Hz.
文摘Precessing ball solitons (PBS) in a ferromagnet during the first order phase transition induced by a magnetic field directed along the axis of anisotropy, while the additional action of high-frequency field perpendicular to the main magnetic field, are analyzed. It is shown that the spatial motion of solitons, associated with thermal fluctuations in the crystal, does not destroy the equilibrium of self-organized PBS.
文摘Precessing ball solitons (PBS) in a ferromagnet during the first order phase transition is induced by a magnetic field directed along the axis of anisotropy, while the action of the periodic field perpendicular to the main magnetic field has been analyzed. Under these conditions, the characteristics of arising equilibrium PBS are uniquely determined by the frequency of the periodic field, but the solitons with other frequencies are impossible. For such structure, the entropy increase connected with dissipation is compensated by the decrease of the entropy due to the external periodic field. It is shown that the equilibrium PBS are essentially the “self-organizing systems” that can arise spotaneously in a metastable state of ferromagnet.
