Magnetic and electrical properties of spin valve with single and double specular oxide layers

Abstract

Appropriate oxide capping on a spin valve significantly improved electrical and magnetic properties. The interlayer exchange coupling oscillated in the thickness range of a Cu spacer (between 20 and 30 Å). The coupling was antiferromagnetic and it allowed us to reduce the Cu spacer down to 20 Å without sacrificing the good properties of the spin valve. The improvement is due to enhanced specular reflection at the interface between the magnetic and the oxide layer and to less current shunting through the Cu spacer. In particular, the Cu in the capping acts as a filter controlling the diffusion of oxygen, which has led to the soft magnetic properties. Embedding an additional thin oxide layer into the pinned layer further improved the magnetoresistance response of the spin valve. Confinement of electrons between two oxides helps increase the occurrence of spin-dependent scattering. As a result, high giant magnetoresistance values resulted. The coupling oscillated from ferromagnetic to antiferromagnetic as a function of thickness of the Cu spacer. No significant bias in the coupling was observed and this lack of bias can be attributed to the smoothness of the interfaces. The oscillations were observable due to amplified Ruderman–Kittel–Kasuya–Yoshida-like coupling by strong reflection at the interfaces of the oxides.