Magnetic properties in a partially oxidized nanocomposite of Cu-CuCl

TL;DR

This study investigates the magnetic properties of partially oxidized Cu-CuCl nanocomposites, revealing ferromagnetic-like behavior below a certain temperature due to surface CuO and the influence of Cl- ions on magnetic susceptibility.

Contribution

It provides new insights into the magnetic behavior of Cu-CuCl nanocomposites with core-shell structures, highlighting the role of surface CuO and chloride ions in magnetic phenomena.

Findings

Ferromagnetic-like hysteresis below freezing temperature.

Paramagnetic response at high fields and T > TF.

Enhanced magnetic susceptibility with Cl- ions at low temperatures.

Abstract

Magnetism of a very thin antiferromagnetic (AFM) surface CuO has been investigated with the partially oxidized nanocomposites of Cu-CuCl, ~ 200 nm. The samples are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, X-ray-excited Auger electron spectroscopy, transmission electron microscope and magnetic measurements. The characterizations indicate that the composites have a core-shell structure. Before the oxidation, it is (Cu)core/(CuCl)shell, and after the oxidation, (Cu)core/(Cu2O+CuCl+minuteCuO)shell. The magnetic measurements have revealed that a ferromagnetic (FM) like open hysteresis exists at the temperature below the freezing point, TF. In the high field region, a paramagnetic (PM) response appears without showing a sign of saturation. Also, the field dependent magnetization (M-H) measurement is PM-like at T > TF. These interesting magnetic properties are evident to arise from the AFM CuO on the outer surface. They are attributed to the uncompensated surface spins of Cu2+ and the effect of surface random potential. More interestingly, the magnetic susceptibility is greatly enhanced in the presence of Cl- anions at T < TF, according to the field-cooled/zero-field-cooled (FC/ZFC) measurements. This further supports the point that the disorder or frustration effect of the impurity would reduce the AFM ordering of CuO and increase the level of uncompensated spins.