Magnetic structure in the amorphous (FexNd1 x)0;6B0;4 nanoparticle compounds

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

Conferencia; At the Frontiers of Condensed Matter IV; 2008

CNEA-Centro Atómico Constituyentes

We studied the internal magnetic order in several samples of amorphous nanoparticles of Fe-Nd-B ob-tained by chemical route. The samples chosen have diferent relative composition Fe/Nd in order to study the eect of chemical composition in the magnetic properties. Magnetic characterisation was made as a function of temperature and applied magnetic field.In every case these measurements can be described as a ferromagnetic contribution which saturates, charac-teristic of ferromagnetic monodomains, plus a param-agnetic one. Experimental results are described by a simple model which represents the saturated magneti-sation by the Bloch law, and the paramagnetic one, by the Curie law. This model allowed us to study thenanoparticle behaviour as a function of the applied field and temperature for dierent chemical composi-tions. The fact that the magnetisation can be split in two components is an evidence of the internal mag-netic structure of the particles, which is analysed in the frame of the core-shell model. The behaviour of the coercive eld, Hc, also supports the picture of a core-shell magnetic structure.