Theoretical Study On Magnetic Properties And Magnetic Transport Properties Of Heusler Alloys

Two-dimensional（2D）magnetic materials have attracted extensive attention because of their potential applications in spintronic devices,such as high density magnetic recording media,magnetic memory,and magnetic storage devices.One advantage of 2D magnetic materials is their small size that can meet the demand for the miniaturization of spintronic devices.Another advantage is their high tunability subject to external means,such as magnetic field,electrostatic doping,gate voltage,electrostatic doping.and so on.However,2D magnetic materials are still rare and difficult to synthesize.In addition to 2D magnetic materials,2D magnetism can also be realized on the surface of three-dimensional（3D）materials.Nowadays,it is reported that nonmagnetic Heusler semiconductors,such as Co Cr Ti P,Fe Mn Ti P,and Co Mn VAl,show a rare coexistence of metallicity and magnetism at the surface of their corresponding slabs.such localized magnetic moments are easy to be tuned by the external means.The electrical manipulation of magnetization is appealing to the relevant experiment and spintronic device.In this paper,we focus on the electrical and magnetic properties of a thin film cleaved from the nonmagnetic half-Heusler compound Co Ti Sb.By means of the first-principles calculations,we find that the surface of Ti Sb termination possesses ferrimagnetism with a magnetic moment of 0.35（0.49）μ_Bper unit cell without（with）Hubbard U,which can persist below the Curie temperature of 48（54）K.What is more,such a surface magnetism can be tuned to nonmagnetism by gate-induced hole doping with a concentration of₀n～2.83×10¹⁴(3.55×10¹⁴)cm^-2.This magnetic tunability of the Co Ti Sb slab provides a platform to realize the pseudo-spin valve with both the magnetic electrodes and nonmagnetic space layer made of the same material without hetero-interfaces.In the next work,by using Heusler materials,we construct a magnetic tunnel junction Fe₂Cr Si/Fe₂TiSi/Fe₂Cr Si.The stability of tunnel junction is proved by the calculation of interface forming energy,and the spin dependent transport properties show significant theoretical Tunneling magnetoresistance（TMR）which can reach up to 10¹⁰%.At present,we are still studying the contribution of each element to the scattering and calculating the TMR under the bias,hoping the device can maintain a relatively satisfactory TMR under a bias.