Magnetic devices have become increasingly integrated into modern technology as they enable technologies as varied as computer hard drives, RF circulators, and medical diagnostic equipment. Electrically controlling magnetism in the small scale, however, has always been difficult due to the inefficiencies of generating the localized nanoscale magnetic fields necessary to precisely control such devices. Traditional macroscale methods (such as simple Oersted fields) fail when scaled to the sizes of modern device components, and even the most efficient established techniques (spin transfer torque, spin hall effect) are current-based and thus dissipate substantial power when used to switch magnetic elements.
Recent work in the field of multiferroic materials has opened the potential for using voltage, rather than current, to manipulate magnetism in these systems, potentially increasing the efficiency of nanoscale magnetic control by several orders of magnitude. In this thesis, we explore the Acoustically Driven Ferromagnetic Resonance effect in composite strain-coupled multiferroic bilayers. This technique allows for a voltage-driven piezoelectric excitation to drive magnetostrictive thin films into resonance with a much greater coupling efficiency than is possible using traditional methods. By leveraging this enhanced coupling, it is possible to develop a number of novel devices based on this interaction that span a number of extremely important commercial fields.
This thesis experimentally explores the dependence of this effect on a number of factors such as operating frequency, input power, magnetic element size and thickness, and magnetic element composition. We also study three high-potential applications for this technology: magnetic sensing, antenna miniaturization, and room-temperature coupling to quantum systems - specifically diamond nitrogen-vacancy centers. While some of these applications are far from commercial readiness, we are able to demonstrate proof-of-concept examples for each of these concepts that demonstrate that the core concept is valid and is worth further exploration.
Acoustically Driven Ferromagnetic Resonance for Device Applications
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