Abstract
In this work, 30nm Fe2Cr1-xCoxSi (FCCS) magnetic films were deposited on Cr buffered MgO (100) substrates by sputtering. Fe2Cr0.5Co0.5Si exhibits the largest magnetization and optimal ordered L21 cubic structure at in-situ annealing temperature (Tia) of 450°C. The Co composition dependence of crystalline structures, surface morphology, defects, lattice distortions and their correlation with the magnetic properties are analyzed in detail. The Co-doped samples show in-plane M-H loops with magnetic squareness ratio of 1 and increasing anisotropy energy density with Co composition. Appropriate Co doping composition promotes L21 phase but higher Co composition converts L21 to B2 phase. Doping effect and lattice mismatch both are proved to increase the defect density. In addition, distortions of the FCCS lattice are found to be approximately linear with Co composition. The largest lattice distortion (c/a) is 0.969 for Fe2Cr0.25Co0.75Si and the smallest is 0.983 for Fe2CrSi. Our analyses suggest that these tetragonal distortions mainly induced by an elastic stress from Cr buffer account for the large in-plane anisotropy energy. This work paves the way for further tailoring the magnetic and structural properties of quaternary Heusler alloys.
Highlights
INTRODUCTIONThe in-plane anisotropy could linearly change with lattice deformation
Heusler alloys are promising candidates for spintronic applications such as magnetic random access memory (MRAM) due to their low damping, high spin polarization and high Curie temperature.1–4 Co-based Heusler alloys have been extensive investigated,5–8 their large magnetizations are not favorable to reduce the switching current density in device applications
We investigated the effect of T ia for Fe2Cr0.5Co0.5Si and determined the optimal annealing temperature
Summary
The in-plane anisotropy could linearly change with lattice deformation.. The annealing temperature dependence of lattice strains and its effect on magnetic anisotropies of Co-based Heusler alloy has been studied.. The doping dependence of defect and strain in Fe-based Heusler alloy is still lacking. Some defects or misfit in Heusler alloys can affect other properties such as resistivity and spin polarization.. It’s important to study strain or lattice distortion in the FCCS. We have previously demonstrated high perpendicular and in-plane tunnel magnetoresistance ratio (TMR) by optimizing FCCS in magnetic tunnel junction (MTJ).. We provide a detailed investigation of the structural and magnetic properties of Cr buffered FCCS dependent on T ia and Co doping composition. The defects and lattice distortion affected by Co doping are discussed
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