Magnetization processes in Nd60Fe30Al10 partially amorphous alloys

Abstract Hysteresis and relaxation properties of Nd 60 Fe 30 Al 10 partially amorphous alloys, processed by melt spinning at 5 m/s (V5), 10 m/s (V10) and 20 m/s (V20), are investigated. Specimens V20 show two-step hysteresis loops while relatively square loops, exhibiting magnespring effects, are found in samples V5. In these latter microstructures, the demagnetization process has associated a nearly constant fluctuations field of μ 0 H f =14.5 mT , and a characteristic activation length l ac =7 nm . These values are similar to those obtained for V10 and V20 at the hard irreversible susceptibility peak: 13.1 mT, 7.3 nm (V10) and 13.5 mT, 7.1 nm (V20), respectively. In specimens V5, hysteresis and thermal relaxation are controlled by the same distribution of energy barriers and the results obtained are consistent with a reversion process involving a nucleation mechanism in a magnetic grain of size l mg ∼ l ac , with l mg the exchange length in the amorphous phase. This characteristic length is estimated by considering the amorphous phase as a two-phase magnetic composite in which the hard Fe-rich clusters are coupled by exchange interactions, mediated by a surrounding Nd-rich phase.