# Micromagnetic Simulations for Coercivity Improvement through Nano-Structuring of Rare-Earth Free L1$_0$-FeNi Magnets

## TL;DR

This study uses micromagnetic simulations to explore how nano-structuring L1$_0$-FeNi magnets can enhance coercivity and energy product, aiming to develop rare-earth-free permanent magnets.

## Contribution

It demonstrates the potential of nano-structuring L1$_0$-FeNi to improve magnetic properties, providing specific energy product estimates for different grain shapes.

## Key findings

- Nano-structured L1$_0$-FeNi can reach up to 252 kJ/m$^3$ energy product.
- Different grain shapes yield varying maximum energy products.
- Small coercive fields limit the maximum energy product achievable.

## Abstract

In this work we investigate the potential of tetragonal L1$_0$ ordered FeNi as candidate phase for rare earth free permanent magnets taking into account anisotropy values from recently synthesized, partially ordered FeNi thin films. In particular, we estimate the maximum energy product ($BH$)$_\mathrm{max}$ of L1$_0$-FeNi nanostructures using micromagnetic simulations. The maximum energy product is limited due to the small coercive field of partially ordered L1$_0$-FeNi. Nano-structured magnets consisting of 128 equi-axed, platelet-like and columnar-shaped grains show a theoretical maximum energy product of 228 kJ/m$^3$, 208 kJ/m$^3$, 252 kJ/m$^3$, respectively.