Theses and Dissertations at Montana State University (MSU)
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Item Epitaxial thin film deposition of magnetostrictive materials and its effect on magnetic anisotropy(Montana State University - Bozeman, College of Letters & Science, 2012) McClure, Adam Marc; Chairperson, Graduate Committee: Yves U. Idzerda; Steven Albert, Tino Jaeger, Hongyan Li, Paul Rugheimer, Juergen A. Schaefer and Yves U. Idzerda were co-authors of the article, 'Properties of single crystal Fe 1-xGa x thin films' in the journal 'Journal of applied physics' which is contained within this thesis.; Elke Arenholz and Yves U. Idzerda were co-authors of the article, 'Ferrimagnetic ordering of single crystal Fe 1-xGa x thin films' in the journal 'Journal of vacuum science and technology A' which is contained within this thesis.; Hongyan Li and Yves U. Idzerda were co-authors of the article, 'Magnetostrictive effect in single crystal Fe 1-xGa x thin films' in the journal 'Journal of applied physics' which is contained within this thesis.; Paul Rugheimer and Yves U. Idzerda were co-authors of the article, 'Magnetic and structural properties of single crystal Fe 1-xZn x thin films' in the journal 'Journal of applied physics' which is contained within this thesis.Magnetostriction means that the dimensions of a material depend on its magnetization. The primary goal of this dissertation was to understand the effect of magnetostriction on the magnetic anisotropy of single crystal magnetostrictive thin films, where the epitaxial pinning of the material to a substrate could inhibit its conversion to new dimensions. In order to address this goal, several Fe-based binary alloys were deposited onto various substrates by molecular beam epitaxy. The samples were characterized by an array of techniques including electron diffraction, Rutherford backscattering, vibrating sample magnetometry, ferromagnetic resonance, and x-ray absorption spectroscopies. The attempted growths of crystalline magnetostrictive thin films resulted in successful depositions of Fe 1-xGa x and Fe 1-xZn x. Depositions onto MgO(001) substrates result in an in-plane cubic magnetic anisotropy, as expected from the cubic symmetry of the Fe-based thin films, and a strong out-of-plane uniaxial anisotropy that forces the magnetization to lie in the plane of the films. Depositions onto ZnSe/GaAs(001) substrates feature an additional in-plane uniaxial anisotropy. The magnitudes and signs of the in-plane anisotropies depend on the Ga content. Furthermore, the cubic anisotropy constant of Fe 1-xGa x samples deposited onto MgO substrates switches sign at a lower Ga concentration than is seen in bulk Fe 1-xGa x. The effect on the magnetic anisotropy of depositing a magnetostrictive material as an epitaxial thin film is influenced by the material's magnetostrictive properties and the substrate upon which it is deposited. In particular, pinning a magnetoelastic material to a substrate will modify its cubic anisotropy, and depositions on substrates compliant to an anisotropic strain relaxation may result in a strong in-plane uniaxial anisotropy.Item Control of the spin relaxation and magnetic anisotropy in Fe 1-x Ga x/ZnSe systems(Montana State University - Bozeman, College of Letters & Science, 2011) Li, Hongyan; Chairperson, Graduate Committee: Yves U. IdzerdaMagnetostrictive 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.