First-principle Study On The Electronic Structure And Magnetic Properties Of Fe_3-xM_xO₄

Fe₃O₄ as a typical representative of the spinel ferrite have attractedgreat interests for the potential technological application for spintronic devices because they are simple structure,phase structure stability,oxidation-resistivity and 100%spin polarization,,magnetic resistance effect,hall effect.But it is still limited in spintronics and storage due to resistivity and magnetoresistance is lower.This article based on density-function theory?Vienna ab initial simulation package?,GGA+U method is used to calculate the electronic structure and magnetic properties of Fe₃O₄.And the effects of different lattice constant substrates on the microstructure,magnetic properties and carrier concentration of epitaxially grown Fe₃O₄ thin films were investigated.also calculate the magnetic properties of the electronic structure of the system which magnetic metal elements and nonmagnetic metal elements doped Fe₃O₄.Calculation results show that the magnetic Fe₃O₄ mainly comes from the electronic Fe3d orbit,tetrahedral sites and octahedral sites Fe magnetic moment an inverse parallel arrangement,the magnetic moments of Fe₃O₄ are 4.0?B,and the Fermi surface has a spin-down electronic state with half-metallic properties.When the lattice constant mismatch between the substrate and the Fe₃O₄ thin film is less than 5%,the total magnetic moment of the system is invariable,and the magnetic moment of each atom varies with the pressure of the Fe₃O₄ thin film.Stress increases,with the increase of tensile stress increases.Under the action of stress,the charge localization degree becomes lower and the carrier concentration becomes smaller.The calculation of doping of Co shows that the doping of Co ions destroys the hybridization of Fe3d and O2p and the magnetic moment of the cell decreases from 4?B to 3?B.The conductivity of the system changes from half-metal to insulator.The doping calculations of the non-magnetic elements Al and Ti show that the octahedral substitution of Al ions destructs the pd hybridization of the system and significantly reduces the magnetic moment of the system.With the increase of Al ion doping concentration,The conduction band moves to the low energy region,the band gap becomes smaller,and the conductive property changes from half-metal to metal.Ti ions can easily enter the tetrahedral sites,which can greatly improve the performance of the system,not only can obtain high spin polarization,but also improve the original cell magnetic moment and system resistance,which is expected as a spin device injection source candidate material.