Structural and Magnetic Properties of Co-rich bct CoMn Films

TL;DR

This study investigates the enhanced magnetic moments of Co-Mn thin films grown on MgO substrates, revealing substrate-dependent magnetic properties and potential for improved ferromagnetic phase stability.

Contribution

It demonstrates that substrate choice significantly influences the magnetic moments and stability of bct Co-Mn films, offering pathways to optimize ferromagnetic properties in thin-film applications.

Findings

Enhanced atomic magnetic moment of 2.52 μB/atom in Co-Mn films exceeds bulk values.

Substrate selection affects magnetic moments, with smaller lattice constant substrates increasing moments.

Theoretical calculations suggest improved ferromagnetic stability on certain substrates.

Abstract

Thin-films of bct Co$_{1-x}$Mn$_x$ grown by molecular beam epitaxy on MgO(001) were measured to have an enhanced atomic magnetic moment of $2.52 \pm 0.07$ $\mu_\text{B}/\text{atom}$ beyond the pinnacle of the Slater-Pauling curve for Fe$_{1-x}$Co$_{x}$ with a moment of $2.42$ $\mu_\text{B}/\text{atom}$. The compositional variation of the average total moment for thin-film bct Co$_{1-x}$Mn$_x$ alloys is in stark contrast to the historical measurements of bulk fcc Co$_{1-x}$Mn$_x$. These GGA calculations reveal that significant improvements of this ferromagnetic forced bct phase on MgO(001) are possible via substrate selection. For example, bct Co$_{1-x}$Mn$_x$ films on MgO(001) are calculated to have lower atomic moments than those on substrates with smaller lattice constants such as GaAs(001), BaTiO$_3$(110), and SrTiO$_3$(110) which is predicted to increase the average atomic moment up to $2.61$ $\mu_\text{B}/\text{atom}$ and lead to increased structural stability and therefore thicker film growths.