Ordering In A Spin Glass under Applied Magnetic Field

Torque, torque relaxation, and magnetization measurements on a AuFe spin glass sample are reported. The experiments carried out up to 7T show a transverse irreversibility line in the $(H,T)$ plane up to high applied fields, and a distinct strong longitudinal irreversibility line at lower fields. The data demonstrate that for this type of sample, a Heisenberg spin glass with moderately strong anisotropy, the spin-glass-ordered state survives under high applied fields in contrast to predictions of certain ``droplet''-type scaling models. The overall phase diagram closely resembles those of mean field or chiral models, both of which have replica symmetry breaking transitions.