Magnetization-induced second-harmonic generation of cobalt and cobalt oxide nanoparticles

Abstract

Magnetization-induced second-harmonic generation (MSHG) technique in transverse Kerr configuration is used to explore the nonlinear magneto-optical properties of cobalt and cobalt oxide nanoparticles at room temperature. The nanoparticles are deposited on Si (100) substrate by a RF magnetron sputtering system at room temperature. The STM image of the studied sample indicates that the cobalt particle size is in the range of 10 nm to 30 nm. MSHG technique investigates their magnetic anisotropy property and determines their crystal and magnetic symmetry. The pure cobalt nanoparticle thin films have a large nonlinear Kerr rotation response with a low external magnetic field. The increase of coercivity field, Hc, in the cobalt oxide nanoparticle thin films, can be attributed to the strong interaction between the ferromagnetic cobalt and anti-ferromagnetic cobalt oxide interface. It is found that the magnetic anisotropy is due to the shape anisotropy of cobalt nanoparticle thin film and their interaction. The magnetization reversal process of cobalt nanoparticles involves the rotation of the magnetic moment in the surface plane but not the surface normal plane. This study aims to reveal the important information regarding the magnetization orientation in the ferromagnetic materials and their heterostructures.