Strong perpendicular magnetic anisotropy in epitaxial D022-Mn3+xGa ultrathin films

Abstract

Ferrimagnets are highly sought-after materials thanks to their strong perpendicular magnetic anisotropy (PMA) and low magnetization. For example, they are promising materials for current-induced magnetization switching applications. Ferrimagnetic D022-Mn3Ga integrates these properties with a low damping constant and a high Curie temperature. Here, we report a complete analysis of the magnetization and the effective PMA evolution with the thickness of the epitaxial D022-Mn3+xGa ultrathin films. The crystals were grown by magnetron sputtering following two methods: reactive deposition epitaxy and solid phase epitaxy. We found that the uniaxial PMAs and the thickness of the dead magnetic layers differ strongly upon the employed growth method, while saturation magnetizations remain unchanged. Structural defects at the interface due to lattice mismatch and growth method, explain our results. We expose objective estimations of the thermal stability factor Δ, based on the effective PMA in the ultrathin film context. Taking into account our results, D022-Mn3+xGa, in this form, can be employed as the free layer on magnetic tunnel junctions.