Carbon-induced magnetic properties and anomalous Hall effect in Co2Mn2C thin films with L10 -like structures

Abstract

${\mathrm{Co}}_{2}{\mathrm{Mn}}_{2}\mathrm{C}$ thin films were synthesized via vacuum carburization of the host CoMn alloy films based on a conventional gas-solid reaction to demonstrate the effect of C, a common light element, on the magnetic and spintronic materials. The crystal structure transitioned from the disordered face-centered-cubic CoMn to the $L{1}_{0}$-like ${\mathrm{Co}}_{2}{\mathrm{Mn}}_{2}\mathrm{C}$, for which the lattice constant increased from 0.356 to 0.378 nm. The C $1s$ x-ray photoemission spectra of the ${\mathrm{Co}}_{2}{\mathrm{Mn}}_{2}\mathrm{C}$ film indicated hybridization in C-Co and C-Mn and a homogeneous concentration of C in the film. The enhancement of both the saturation magnetization and the anomalous Hall conductivity (${\ensuremath{\sigma}}_{xy}$) was induced by C, attributing to the magnetic transition to the ferrimagnetic spin order. The surface flatness and high ${\ensuremath{\sigma}}_{xy}$ are promising characteristics for spintronic applications such as the spin-anomalous Hall effect. The atom- and spin-resolved density of states (DOS) via first-principles calculations revealed that face-centered Mn(II) and Co could be significantly influenced by C because of p-d hybridization, resulting in enhanced spin polarization of the DOS at the Fermi level of \ensuremath{\sim}0.82. These results demonstrate that the use of C could be an essential way to boost material properties in the future.