Electronic structure and magnetic properties of L1_0 binary alloys

TL;DR

This study systematically investigates the electronic and magnetic properties of L1_0 binary alloys using density functional theory, revealing high anisotropies, specific magnetizations, and Curie temperatures, and examining disorder effects.

Contribution

It provides new insights into the magnetic properties and stability of L1_0 binary alloys, including the effects of disorder and off-stoichiometry, using two different DFT approaches.

Findings

High magnetocrystalline anisotropies in CoNi, MnAl, MnGa

Curie temperatures exceeding 900 K for FeNi and CoNi

Disorder reduces anisotropies and Curie temperatures

Abstract

We present a systematic study of the magnetic properties of L1$_0$ binary alloys FeNi, CoNi, MnAl and MnGa via two different density functional theory approaches. Our calculations show large magnetocrystalline anisotropies in the order $1~\text{MJ/m}^3$ or higher for CoNi, MnAl and MnGa while FeNi shows a somewhat lower value in the range $0.48 - 0.77 ~\text{MJ/m}^3$. Saturation magnetization values of $1.3~\text{MA/m}$, $1.0~\text{MA/m}$, $0.8~\text{MA/m}$ and $0.9~\text{MA/m}$ are obtained for FeNi, CoNi, MnAl and MnGa respectively. Curie temperatures are evaluated via Monte Carlo simulations and show $T_\text{C}=916~\text{K}$ and $T_\text{C}=1130~\text{K}$ for FeNi and CoNi respectively. For Mn-based compounds Mn-rich off-stoichiometric compositions are found to be important for the stability of a ferro or ferrimagnetic ground state with $T_\text{C}$ greater than $600~\text{K}$. The effect of substitutional disorder is studied and found to decrease both magnetocrystalline anisotropies and Curie temperatures in FeNi and CoNi.