Phase transitions in random anisotropy magnets

We report a study of magnetic properties and phase transitions in random anisotropy glasses rich in the rare-earth elements Gd, Tb and Nd. For the Gd glass, which has a small magnetic anisotropy, we find an extremely large, possibly infinite, susceptibility below 120 K and no intrinsic spontaneous magnetization. Below 55 K an hysteretic state develops. The Tb and Nd glasses, both of which have large anisotropy, exhibit transitions to a speromagneic state and they do not show an infinite susceptibility phase. The results are discussed in terms of recent theoretical predictions concerning phase transitions in the presence of random magnetic anisotropy.