Research On The Influence Of Substrate On The Microstructure And Magnetic Properties Of MnGa Thin Film

MnGa alloys with high perpendicular magnetic anisotropy?spin polarization?low Gilbert damping constant and tunable saturation magnetization,is a promising candidate for high density magnetic storage media and spintronics application.Using first principle calculation,we have investigated the influence of substrates on the lattice constants?atomic magnetic moments and magnetic anisotropic energy of Mn_0.625Ga_0.75 thin film,and perturbation theory is applied to interpret qualitatively these results.Meanwhile,MnGa thin films were prepared on MgO?001??SrTiO₃?001??Si?001?and amorphous SiO₂ substrates using magnetron sputtering,respectively.The crystal structure of these samples was determined by X-ray diffraction?XRD?with CuK?radiation,the surface morphology was measured by atomic force microscope?AFM?,and the magnetic parameters were analyzed by vibrating sample magnetometer?VSM?,to confirm the effects of substrates on magnetic properties of MnGa thin films.Calculation reveals that c/a decreases linearly as the lattice constant,referred to as a,increases,with a equals to 3.82?in ground state,with a volume of 105?³ in unit cell and saturation magnetization of 578emu/cc,perpendicular magnetic anisotropy constant as high as 19.7Merg/cc,respectively.The atomic magnetic moments of Mn at Wyckoff position 4d decrease while those of the others increase as a increases,leading to the decrease of total magnetic moments and saturation magnetization.Moreover,the films exhibit perpendicular magnetic anisotropy?PMA?,and the PMA is enhanced with increasing lattice constants a,when a increases from 3.80?to 4.00?,the perpendicular magnetic anisotropy constant increases from 19.2Merg/cc to 23.8Merg/cc,due to the enhancement of the interaction between electrons of different spin states.The experimental results show that the surface roughness of MnGa film increases with the increase of lattice mismatch,and the roughest surface is obtained in MnGa thin film deposited on amorphous SiO₂;MnGa thin films deposited on MgO?001?,SrTiO₃?001?and Si?001?exhibit PMA enhanced with increasing a,while the MnGa film grown on the amorphous SiO₂ shows isotropic magnetic properties.