Magnetic behavior of oxide passivated (Fe0.85Nd0.15)0.6B0.4 amorphous nanoparticles

Abstract

We report on magnetic amorphous (Fe0.85Nd0.15)0.6B0.4 nanoparticles showing an enhanced thermagnetic stability regarding to their size, with a blocking temperature higher than room temperature. Magnetization and Mössbauer spectroscopy results suggest that the ideally spherical nanoparticles conformation is almost equally distributed between an ordered core and an iron oxide shell (Fe2O3). Magnetization measurements are described by a phenomenological model comprising a ferromagnetic core represented by the Bloch´s law and a magnetically disordered contribution obeying the Curie law. The interaction of the core with the oxide shell would be enough to thermally stabilize the nanoparticles against superparamagnetism.