Absence of Hysteresis in the Heat Capacity of the Three-Dimensional Random-Field Ising Model

Heat capacity measurements on the prototypical three-dimensional random-field Ising model compound Fe0.58Zn0.42F2 have been performed in both of the field-cooling (FC) and zero-field-cooling (ZFC) procedures. There is no evidence of hysteresis between the FC and ZFC protocols within the experimental accuracy. The absence of hysteresis is interpreted based on a magnetic field (H)-temperature (T) phase diagram in which a metastability region exists between the Neel temperature line Tn(H) and Hc1(T), the latter being the lowest critical field line for the local spin flips.