Role of dipolar interactions in a system of Ni nanoparticles studied by magnetic susceptibility measurements

Abstract

The role of dipolar interactions among Ni nanoparticles NPs embedded in an amorphous SiO2 /C matrix with different concentrations has been studied performing ac magnetic susceptibility ac measurements. For very diluted samples, with Ni concentrations 4 wt % Ni or very weak dipolar interactions, the data are well described by the Néel-Arrhenius law. Increasing Ni concentration to values up to 12.8 wt % Ni results in changes in the Néel-Arrhenius behavior, the dipolar interactions become important, and need to be considered to describe the magnetic response of the NPs system. We have found no evidence of a spin-glasslike behavior in our Ni NP systems even when dipolar interactions are clearly present.