Magnetizacion processes in Nd60Fe30Al10 partially amorphous alloys

O. V. BILLONI; S. E. URRETA; L. M FABIETTI

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

ELSEVIER SCIENCE BV

Año: 2003 vol. 265 p. 222 - 233

0304-8853

Hysteresis and relaxation properties of Nd60Fe30Al10 partiallyamorphous alloys, processed bymelt 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 relativelysquare loops, exhibiting magnespring effects, are found in samples V5. In these latter microstructures, thedemagnetization process has associated a nearlyconstant fluctuations field of m0Hf ¼ 14:5mT; and a characteristicactivation length lac ¼ 7 nm: These values are similar to those obtained for V10 and V20 at the hard irreversiblesusceptibility peak: 13.1 mT, 7.3nm (V10) and 13.5 mT, 7.1nm (V20), respectively. In specimens V5, hysteresis andthermal relaxation are controlled bythe same distribution of energybarriers and the results obtained are consistent witha reversion process involving a nucleation mechanism in a magnetic grain of size lmgBlac; with lmg the exchange lengthin the amorphous phase. This characteristic length is estimated byconsidering the amorphous phase as a two-phasemagnetic composite in which the hard Fe-rich clusters are coupled byexchange interactions, mediated by a surroundingNd-rich phase.