X-Ray and Neutron Scattering, Magnetization, and Heat Capacity Study of the 3D Random Field Ising Model

Abstract

Magnetic x-ray and neutron scattering, SQUID magnetometry, and heat capacity measurements of F${\mathrm{e}}_{0.5}$Z${\mathrm{n}}_{0.5}$${\mathrm{F}}_{2}$ in a field are presented. The zero field cooled (ZFC) x-ray results exhibit no true phase transition. Discordantly, the temperature derivative of the uniform magnetization $(M)$ displays a peak, which has previously been interpreted as reflecting random field Ising model critical heat capacity. We demonstrate that the ZFC $dM/dT$ peak, in common with other indirect heat capacity measurements, instead reflects the effects of nonequilibrium ZFC long range order.