# Magnetic Field Dependence of Spin Glass Free Energy Barriers

## TL;DR

This study investigates how magnetic field variations affect free energy barriers in a spin glass, confirming theoretical predictions through experimental measurements of magnetization dynamics in a thin amorphous film.

## Contribution

It provides experimental validation of the magnetic field dependence of spin glass free energy barriers, supporting the barrier model predictions.

## Key findings

- Activation energy increases when magnetic field decreases.
- Change in energy barriers is proportional to the square of field variation.
- Experimental results agree quantitatively with theoretical barrier model.

## Abstract

We measure the field dependence of spin glass free energy barriers in a thin amorphous Ge:Mn film through the time dependence of the magnetization. After the correlation length $\xi(t, T)$ has reached the film thickness $\mathcal {L}=155$~\AA~so that the dynamics are activated, we change the initial magnetic field by $\delta H$. In agreement with the scaling behavior exhibited in a companion Letter [Janus collaboration: M. Baity-Jesi {\it et al.}, Phys. Rev. Lett. {\bf 118}, 157202 (2017)], we find the activation energy is increased when $\delta H < 0$. The change is proportional to $(\delta H)^2$ with the addition of a small $(\delta H)^4$ term. The magnitude of the change of the spin glass free energy barriers is in near quantitative agreement with the prediction of a barrier model.