  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.
