Spin reversal magnetic transistion in (Fe0.85Nd0.15)0.6B0.4 nanoparticles

M. TORTAROLO; R.D. ZYSLER; H. ROMERO

Buenos Aires

Workshop; At the frontiers of condensed matter III, FCM 2006; 2006

Centro Atómico Constituyentes, CNEA

We have synthesised and magnetically characterised (Fe0.85Nd 0.15)0.6B0.40 amorphous nanoparticles (»7 nm). The (Fe0.85Nd 0.15)0.6B0.40 alloy, very well known because its technological applications, shows several anomalies which consist  in an evident reduction of the saturation magnetisation and coercive field for this particular sample compared to its neighbouring compositions. We studied both dispersed and powder samples, the dispersed one (in a non-magnetic matrix) let us study the intrinsic magnetic order inside the nanoparticle, whereas the in the powder one the particles interact among them and the internal order is somehow frustrated. The observed anomalies seem to vanish for temperatures higher than RT and are present in dispersed and powder samples. Coercive field follows the magnetic moment tendency confirming that the anysotropy is mainly due to the shape of the particles. We associate this behaviour with a spin reversal inside the particle for this composition which tends to reduce the magnetic moment of the particles, leading to the observed decreasing of saturation magnetisation and coercive field relative to the values of the neighbouring compositions.