# Magnetoelasticity of $\mathrm{Co_{25}}\mathrm{Fe_{75}}$ thin films

## TL;DR

This study measures the magnetoelastic properties of Co-Fe thin films, revealing negative magnetostriction and highlighting their potential for micromechanical magnonic applications.

## Contribution

It provides the first detailed measurement of magnetostrictive constants for specific Co-Fe thin films, contrasting bulk properties and identifying promising materials for sensors.

## Key findings

- Negative magnetostriction constants for thin films.
- Co25Fe75 combines low damping with sizable magnetostriction.
- Potential applications in sensors and hybrid phonon-magnon systems.

## Abstract

We investigate the magnetoelastic properties of $\mathrm{Co_{25}}\mathrm{Fe_{75}}$ and $\mathrm{Co_{10}}\mathrm{Fe_{90}}$ thin films by measuring the mechanical properties of a doubly clamped string resonator covered with multi-layer stacks containing these films. For the magnetostrictive constants we find $\lambda_{\mathrm{Co_{25}}\mathrm{Fe_{75}}}=(-20.68\pm0.25)\times10^{-6}$ and $\lambda_{\mathrm{Co_{10}}\mathrm{Fe_{90}}}=(-9.80\pm0.12)\times10^{-6}$ at room temperature. In stark contrast to the positive magnetostriction previously found in bulk CoFe crystals. $\mathrm{Co_{25}}\mathrm{Fe_{75}}$ thin films unite low damping and sizable magnetostriction and are thus a prime candidate for micromechanical magnonic applications, such as sensors and hybrid phonon-magnon systems.