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 ξ(t,T) has reached the film thickness L=155  A so that the dynamics are activated, we change the initial magnetic field by δH. In agreement with the scaling behavior exhibited in a companion Letter [M. Baity-Jesi et al., Phys. Rev. Lett. 118, 157202 (2017)PRLTAO0031-900710.1103/PhysRevLett.118.157202], we find that the activation energy is increased when δH<0. The change is proportional to (δH)^{2} with the addition of a small (δH)^{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.