Interparticle Interactions in (Fe1-x Nix)100-y By Magnetic Nanoparticles

ROMERO HÉCTOR; ORTEGA A.; ZYSLER ROBERTO; RAMOS CARLOS; DE BIASI EMILIO; FIORANI DINO

Cartagena,Colombia

Simposio; Simposio Latinoamericano de Física del Estado Sólido (XV SLAFES); 1999

In order to study the effect of interparticle interactions the magnetic properties of amorphous (Fe1-x Nix)100-y By nanoparticles (0.25<x<0.75 and y » 0.50) have been investigated by magnetization measurements in a homogeneous dispersion of particles in a PVP polymer and in powder samples. The dispersed samples show the characteristic behaviour of an assembly of independent nanosized particles, characterized by a narrow size distribution, with a sharp maximum of zero field cooled (ZFC) magnetization whereas the field cooled (FC) magnetization increases continuously with the decreasing temperature. The magnetization in the superparamagnetic regime is satisfactorily fitted to a superposition of Langevin functions due to the volume distribution. On other hand, in the powder samples, where the strong interactions are expected, the MZFC shows a wider maximum with a significant increase of the temperature at which it occurs and MFC presents a plateau at low temperature. The magnetization curves for the powder samples can be fitted to a Langevin function if interparticle interactions are taken into account by introducing a mean-field-like term in the argument.