Anomalous magnetic viscosity in bulk-amorphous materials

The demagnetization processes and the magnetic viscosity have been studied on a bulk-amorphous Nd 60 Fe 30 Al 10 rod at room temperature. Many unique magnetic properties have been found in this novel hard magnetic material. A clear hysteresis was present on the minor loops, though the total and irreversible susceptibilities exhibited single-phase magnet behavior. A signi"cant magnetic viscosity was evident at positive "elds. A large magnetic viscosity was found at negative "elds close to the coercivity. The time-dependent magnetization curves were not logarithm-linear and could be well "tted with a logarithm power series with N"6. The #uctuation "eld was strongly dependent on the magnetic "eld. The activation volume was calculated to be 15}60]10~18 cm3. The magnetic viscosity on the minor loops was measured. A non-monotonic behavior was found. ( 1999 Elsevier Science B.V. All rights reserved. PACS: 75.60.Lr; 75.60.Ej; 75.50.B6