Perpendicularly magnetized Mn-Co-Ga-based thin films with high coercive field

TL;DR

This study reports the growth and characterization of Mn-Co-Ga thin films with perpendicular magnetic anisotropy and high coercive fields, revealing structure-dependent magnetic properties and electronic band effects.

Contribution

It demonstrates the tunability of magnetic anisotropy and structure in Mn-Co-Ga films through Co content, supported by experimental and theoretical analysis.

Findings

High uniaxial magnetic anisotropy achieved (1.2 MJ/m^3)

Structural transition from cubic to tetragonal with Co content

Band Jahn-Teller effect linked to van Hove singularity

Abstract

Mn$_{3-x}$Co$_{x}$Ga epitaxial thin films were grown on MgO substrates by magnetron co-sputtering. Structures were tetragonal or cubic depending on Co content. Composition dependence of saturation magnetization and uniaxial magnetic anisotropy $K_u$ of the films were investigated. A high $K_u$ (1.2 MJ m$^{-3}$) was achieved for the Mn$_{2.6}$Co$_{0.3}$Ga$_{1.1}$ film with the magnetic moment 0.84$\mu_B$. Valence band spectra were obtained by hard X-ray photoelectron spectroscopy. Sharp peaks in the cubic case, which were absent in the tetragonal case, prove that a van Hove singularity causes a band Jahn-Teller effect with tetragonal distortion. Observations agree well with the first-principles calculations.