Control of the spin relaxation and magnetic anisotropy in Fe 1-x Ga x/ZnSe systems

Abstract

Magnetostrictive materials will deform under application of a magnetic field. They can be deposited onto various substrates for engineering multifunctional materials, such as integrated micro actuators and multiferroric materials. In this dissertation clamping of a magnetostrive material onto a substrate is demonstrated to give control of the magnetic anisotropy and spin relaxation, to serve as a device with tunable spin relaxation, which uses magnetic field to change the strain and affect the relaxation. The purpose of this thesis is to use ferromagnetic resonance to investigate the interface effects (chemical bonding, interface strain...) on the magnetic anisotropy properties and the magnetic moment relaxation of Fe 1-xGa x /ZnSe for different Ga doping. Fe 1-xGa x has been deposited on ZnSe(001) and ZnSe(110) surfaces. The growth was epitaxial and the crystal axes are perfectly aligned. Angular ferromagnetic resonance in the X-band (9.4 GHz) and Q-band (34.6 GHz) have been done on samples for a veriety of Ga concentrations and thicknesses. The anisotropies for Fe 1-xGa x/ZnSe are found to be composed of a cubic term, an in-plane uniaxial term, and the out-of-plane uniaxial term. The in-plane uniaxial term changes its magnitude and direction with Ga doping while the cubic anisotropy term follows the same trend as the bulk material. The direction switch of the uniaxial anisotropy and the field dependence of the uniaxial term indicated that the uniaxial term is generated from anisotropic strain relaxation.