Loss of long range order in the 3D random field Ising model

We report a synchrotron magnetic x-ray scattering study of the temperature evolution of the magnetic long range order (LRO) of Mn[sub 0.75]Zn[sub 0.25]F[sub 2] in a magnetic field with emphasis on the behavior after zero field cooling (ZFC). We show that with increasing temperature the metastable ZFC LRO vanishes continuously at a temperature well above the equilibrium [ital T][sub [ital N]]; the LRO follows a rounded power law with exponent [beta][sub ZFC]=0.20[plus minus]0.02 and a transition width which scales as [similar to][ital H][sup 2] but with no divergent critical fluctuations. We argue that this behavior is generic to the random field Ising model.