UCLA

Over the last decade, the multiferroic concept has shown considerable success in numerousdevice applications requiring the control of magnetism through voltage-induced strains generated by piezoelectrics coupled to magnetostrictive materials. This approach in the control of magnetism overcomes the associated challenges with device reduction such as decreased energy efficiency by application of voltages instead of currents for operation, leading to the efficient and effective control of magnetism at reduced dimensions. Consequently, there has been an increasing demand for superior thin-film magnetostrictive materials possessing large magnetostriction and lower strain-mediated switching thresholds targeted towards micro and nanoscale multiferroic applications. As materials with these properties are critically vital for future multiferroic applications, further material development coupled with innovative investigation methods are required to meet this demand. This dissertation addresses these scientific requirements by demonstrating relevant developments and investigations on magnetostrictive ferrimagnetic and antiferromagnetic thin films for next generation multiferroic applications. In ferrimagnetic magnetostrictive Tb0.3Dy0.7Fe2 (Terfenol-D) and multilayer iiNi81Fe19/TbFe2 thin films, the atomic level spin and orbital moments are measured by X-ray magnetic circular dichroism (XMCD) to determine the contributions of specific elements towards various components of the magnetic anisotropy and the interface-mediated exchange coupling interaction respectively. In antiferromagnetic γ-FeMn thin films, the influence of stress (i.e. strain) on the orientation of the N�eel vector is studied and an indirect method for the calculation of the saturation magnetostriction λs by AC magnetic susceptibility measurements are demonstrated. The results presented in this dissertation aid in the development of superior energy-efficient and effective magnetostrictive ferri and antiferromagnetic thin films to meet the growing demand of micro and nanoscale magnetic devices for future multiferroic applications.