Magnetic Field Dependence of Spin Glass Free Energy Barriers

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 L = 155 angstrom 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 [M. Baity-Jesi et al., Phys. Rev. Lett. 118, 157202 ( 2017)], we find that the activation energy is increased when dH < 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.