Magneto-Optical Spectroscopy of Nanocomposites (CoFeZr)x(Al2O3)100-x

We present results of magneto-optical investigations of(CoFeZr)(x)(Al2O3)(100-x) film nanocomposites in transverse Kerr effect (TKE) geometry in the spectral range 0.5-4.0eV and magnetic field up to 3.0kOe. Nanocomposites were deposited onto a glass-ceramic substrate by ion-beam sputtering. The TKE response at room temperature strongly depends on the wavelength of light, applied magnetic field H and the volume metallic fraction. From the analysis of the field dependences of TKE at different wavelengths, it follows that in the as-deposited samples, the interaction between nanoparticles at x<30at.% is small and the nanocomposite is an ensemble of superparamagnetic particles; as x increases to 32at.%, a superspinglass-type state arises, then, in the vicinity of 34at.%, along with individual superparamagnetic particles, superferromagnetic regions appear. Long-range ferromagnetic order arises at concentrations x less than the percolation threshold for conductivity x(per)=42.6at.%. In the presence of two different magnetic states in the samples, TKE is not proportional to the magnetization. Both the field dependences at near-infrared region and the spectral dependences of TKE change significantly after annealing of the samples, while the changes in the field dependences of the magnetization are almost imperceptibly.

Automated summary

We investigated the magneto-optical properties of (CoFeZr)(x)(Al2O3)(100-x) film nanocomposites using the transverse Kerr effect (TKE) geometry. The TKE response at room temperature was found to depend on the wavelength of light, magnetic field strength, and the volume metallic fraction. The interaction between nanoparticles was found to be small at low x values, giving rise to a superparamagnetic ensemble, but as x increased, a superspin glass state and superferromagnetic regions appeared. Long-range ferromagnetic order was observed at x concentrations below the percolation threshold for conductivity. After annealing, significant changes were observed in the field and spectral dependence of TKE, while the changes in magnetization were negligible.