# Ab initio study of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L10 FeNi (tetrataenite)

## TL;DR

This study uses relativistic first-principles calculations to analyze the magnetic and electronic properties of L1$_0$ FeNi (tetrataenite), highlighting its potential for rare-earth free permanent magnets.

## Contribution

It provides detailed relativistic calculations of magnetocrystalline anisotropy, Fermi surface, and magnetostriction for L1$_0$ FeNi, offering new insights into its magnetic characteristics.

## Key findings

- Significant discrepancies between calculated and experimental MAE values.
- Detailed analysis of Fermi surface and k-resolved MAE.
- Calculated magnetic moments and magnetostrictive coefficients.

## Abstract

The ordered L1$_0$ FeNi phase (tetrataenite) is recently considered as a promising candidate for the rare-earth free permanent magnets applications. In this work we calculate several characteristics of the L1$_0$ FeNi, where most of the results come form the fully relativistic full potential FPLO method with the generalized gradient approximation (GGA). A special attention deserves the summary of the magnetocrystalline anisotropy energies (MAE's), the full potential calculations of the anisotropy constant $K_3$, and the combined analysis of the Fermi surface and three-dimensional $\mathbf{k}$-resolved MAE. Other calculated parameters presented in this article are the magnetic moments $m_{s}$ and $m_{l}$, magnetostrictive coefficient $\lambda_{001}$, bulk modulus B$_0$, and lattice parameters. The MAE's summary shows rather big discrepancies between the experimental MAE's from literature and also between the calculated MAE's.