Department of Physics, Faculty of Science, Toho University, Miyama 2-2-1, Funabashi City, Chiba 274, Japan
Abstract:
We have investigated critical lines in the H-T plane in a random anisotropy magnet (RAM) a-Dy16Fe84 with a small effective ratio of the anisotropy (D) to the exchange constant (J) by means of ac susceptibility (χ) in static fields H parallel and perpendicular to the ac field. We found that the transverse χ exhibits an anomaly along the irreversible line H(Tf) determined by previous magnetization measurements, while the longitudinal χ does so along a characteristic line H(Ti) in a lower temperature region. Above H(Tf) we also found an extra characteristic line H(Tc). The lines were almost independent of the measured frequency. Both the present results and previous magnetization results suggest that an equilibrium phase transition occurs, and the critical lines analogous to those in Heisenberg spin glasses are present in a weak RAM.