Anomalous magnetic behavior of CuO nanoparticles

TL;DR

This study investigates the unusual magnetic properties of CuO nanoparticles, revealing non-standard antiferromagnetic behavior that differs from typical nanoparticle systems, with unique temperature and field dependence and absence of memory effects.

Contribution

First detailed analysis of the anomalous magnetic behavior of CuO nanoparticles, highlighting their non-superparamagnetic and non-spin-glass-like non-equilibrium properties.

Findings

Bifurcation of FC and ZFC magnetization curves above Ne9el temperature

Absence of the typical ZFC peak in magnetization

Lack of memory effects in CuO nanoparticles

Abstract

We report studies on temperature, field and time dependence of magnetization on cupric oxide nanoparticles of sizes 9 nm, 13 nm and 16 nm. The nanoparticles show unusual features in comparison to other antiferromagnetic nanoparticle systems. The field cooled (FC) and zero field cooled (ZFC) magnetization curves bifurcate well above the N\'eel temperature and the usual peak in the ZFC magnetization curve is absent. The system does not show any memory effects which is in sharp contrast to the usual behavior shown by other antiferromagnetic nanoparticles. It turns out that the non-equilibrium behavior of CuO nanoparticles is very strange and is neither superparamagnetic nor spin glass-like.