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Open Access Publications from the University of California

Excitation, Propagation, and Control of Spin Waves in Magnetic Micro- and Nanostructures

  • Author(s): Chiang, Howard
  • Advisor(s): Khitun, Alexander
  • Balandin, Alexander A.
  • et al.
Creative Commons Attribution 4.0 International Public License

The anticipated end of Moore’s law has accelerated the exploration and development of new approaches to more scalable and more functional logic devices that consume less power. Of the promising technologies that have emerged, magnon spintronics is innovative for its use of magnetic excitation called spin waves. There are several appealing properties inherent in spin waves. For instance, the spin wave can exhibit nanometer wavelengths and micrometer travel distances. This advantage brings spin-based devices with scalability, which can be a substitute and continues the trend of Moore’s law for minimal sized devices. Importantly, spin waves provide Joule-heat-free transfer of information, since the spins do not involve the motion of electrons. This property can prevent excessive energy consumption compared to CMOS. Also, because spin wave devices utilize phase in addition to amplitude, their operations are based on vectors instead of scalar variables, that makes spin waves devices more functional compared to the conventional digital circuitry.

I have dedicated myself to studying the excitation, propagation, and control of spin waves in magnetic micro- and nanostructures. This dissertation is based on my published works, where I contributed to make spin wave devices based on Y3Fe5O12 (YIG) structures, as well as on more recent results based on Ni80Fe20 (Py) nanostructures. YIG and Py are the best materials for prototyping spin wave devices. YIG is an excellent material for building spin wave-based devices because of its extremely low magnetic damping and its status as an insulator. Then, I give results based on Ni80Fe20 (Py) nanostructures. Py has relatively low spin wave damping among conducting materials and is compatible with CMOS technology. Investigation of spin waves in Py nanostructures is expected to lead to the building of scalable and multi-functional devices with capabilities far beyond the scaled CMOS. In this dissertation, I presented spin wave excitation and propagation in magnetic ferrimagnetic and ferromagnetic materials, as well as innovative structural design and spin wave controls for novel applications. I believe this dissertation will contribute greatly to the community.

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