Preparation And Magnetic Properties Of Rare Earth Manganese Oxide Heterojunction

Perovskite-type oxides have attracted much attention due to their rich magnetoelectric properties.Among them,LSMO material,as a room temperature semimetallic material,has a high conduction electron polarities and a low gilbert damping factor,which has great potential in the field of spinner electronics.In order to further explore the high frequency magnetic properties of materials,especially the heterojunction interlayer coupling influence on high frequency magnetic sample,We use low temperature high field VSM and variable temperature ferromagnetic resonance system based on PPMS system,The static and dynamic magnetic properties of LSMO epitaxial films and LSMO/LMO heterojunction materials prepared by PLD method were analyzed,The main work done and the main conclusions reached include:The magnetic properties of the LSMO epitaxial film were analyzed by using the variable temperature FMR system.The results showed that the magnetic moment and the absolute value of the vertical uniaxial anisotropic constant of the sample increased with the decrease of the temperature from room temperature to 100 K,Below the temperature of 100 K,the magnetization and uniaxial anisotropy constants of the sample tend to be constant.The fitting results of the anisotropic equivalent fields of magnetic crystals show that the anisotropic constants of magnetic crystals change linearly with the decrease of temperature.There is a sign change near 225 K,which means the direction of easy magnetization has changed.Through the test,more comprehensive and complete data on the variation of intrinsic magnetism of LSMO thin films with temperature are obtained.The properties of LSMO/LMO heterojunction were tested by means of variable temperature ferromagnetic resonance.The results show that,under the Curie temperature of LMO,ferromagnetic coupling exists between LSMO and LMO,and the absolute value of exchange coupling field increases monotonously with the decrease of temperature.It shows that the interlayer magnetic coupling increases with the decrease of temperature.Compared with the LSMO monolayer film,the resonance field of the heterojunction samples at the same frequency is greatly reduced,that is,the resonance frequency of the heterojunction samples at the same applied magnetic field is significantly increased.The above results show that the interlayer coupling between different ferromagnetic materials can effectively regulate the resonance frequency of materials under specific magnetic fields.The magnetic entropy changes of LSMO films and LSMO/LMO heterojunction materials were tested and analyzed.The results show that by covering LMO overburden,The peak magnetic entropy of LSMO moved from around 350 K to about 300 K,and the working temperature zone of magnetic refrigeration was adjusted to room temperature and broadened to a certain extent.The results show that the Curie temperature can be adjusted by the interface interaction between ferromagnetic material and paramagnetic material,and the suitable working temperature zone of magnetic refrigeration can be obtained.This work is instructive to the optimization of properties of some magnetic refrigerants.In this paper,the author also briefly introduced the process exploration of layered growth of LSMO materials under low oxygen pressure and the preparation of superlattice samples,as well as the exploration work in the preparation of ferromagnetic insulator YIG film.