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Open Access Publications from the University of California

On Magnetoelastodynamics

  • Author(s): Domann, John Patrick
  • Advisor(s): Carman, Greg P
  • et al.
Abstract

This dissertation focuses on the experimental and theoretical strain mediated control of magnetism in bulk and nanoscale structures. Part I of this dissertation primarily provides the first report of mechanical impact on a highly magnetoelastic material. This experimental test analyzed a loading regime well outside of what is normally reported for magnetoelastic materials. In addition to reporting on experimental findings, this chapter also evaluated the creation of a pulsed power device, and predicts magnetoelastic materials can generate power amplitudes similar to those of explosively driven ferromagnetic generators.

Part II of this dissertation analyzed a numerous magnetoelastic and multiferroic devices. The strain mediated control of spontaneous exchange bias is reported. in a Ni-NiO heterostructure. Importantly, it is shown that strain can actively change the sign of the exchange bias, providing a unidirection effect in sharp contrast with the typically uniaxial nature of magnetoelasticity. Also in Part II, an analytic model of a strain powered antenna is provided. This closed form model uses an eigenmode analysis of the longitudinal vibrations of a piezoelectric / piezomagnetic material including electrodynamic coupling. Using this model, the material properties required for a strain powered antenna to radiate more efficiently than a conventional antenna are determined. The last chapter in Part II develops a method for single electrode control of deterministic rotations in a multiferroic motor. Alternating the relative orientation of the magnetic anisotropies leads to deterministic control of a single domain element. This model predicts the minimum strain required to achieve rotation, as well as the dynamic response of such a motor. Lastly, the simulations were used to compute the power density of a multiferroic motor in the absence of viscous damping forces and friction. The estimated power density fills a void left by other technologies, and is a very promising tool for further research.

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