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

TL;DR

This study investigates how dipolar interactions influence the magnetic behavior of Ni nanoparticles in an amorphous matrix, revealing their significance at higher concentrations without inducing spin-glass states.

Contribution

It demonstrates the impact of dipolar interactions on Ni nanoparticle magnetic susceptibility and clarifies their role without evidence of spin-glass behavior.

Findings

Dipolar interactions become significant at Ni concentrations above 4 wt %.

Neel-Arrhenius law describes dilute samples well.

No spin-glass behavior observed despite dipolar interactions.

Abstract

The role of dipolar interactions among Ni nanoparticles (NP) embedded in an amorphous SiO2/C matrix with different concentrations has been studied performing ac magnetic susceptibility Chi_ac measurements. For very diluted samples, with Ni concentrations < 4 wt % Ni or very weak dipolar interactions, the data are well described by the Neel-Arrhenius law. Increasing Ni concentration to values up to 12.8 wt % Ni results in changes in the Neel-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.