Metamagnetic transition in Nd6Fe14−xAlx compounds

Abstract

Ferrimagnetic Nd6Fe14−xAlx compounds with x=3, 3.5, and 4 have been studied by magnetization measurements in fields up to 9 T. Néel temperatures were determined from Mössbauer spectra to be 308, 286, and 239 K, respectively. The net magnetization at T=4.2 K is 3.6 μB/f.u.(x=3), 2.2 μB/f.u.(x=3.5), and zero for x=4. Metamagnetic transitions were observed for all samples, at decreasing critical fields with increasing x. Both the metamagnetic transition hysteresis and the net magnetization decrease with increasing temperature and become negligible near 40 K. The initial susceptibility of Nd6Fe10Al4 shows an anomalous temperature dependence near T=25 K, which might be associated with a spin reorientation. The electrical resistance of the latter compound, measured as a function of applied field, exhibits an abrupt 3% increase at the metamagnetic transition.