Spin Waves on Spin Structures: Topology, Localization, and Nonreciprocity
R. L. Stamps, J.-V. Kim, F. Garcia-Sanchez, P. Borys, G. Gubbiotti, Y. Li, and R. E. Camley
in Spin Wave Confinement II: Propagating Waves, S. O. Demokritov, ed. (Jenny Stanford Publishing, New York, 2017), pp. 219-260.
This chapter discusses the propagation of spin waves along domain walls and consequences of the Dzyaloshinskii-Moriya interaction (DMI) on their dispersion. It also discusses how DMI affects the gap between energies of freely propagating spin waves and spin waves channeled along walls, as well as consequent nonreciprocities. The chapter describes a possibility for creating a mesoscopic metamaterial analogue of domain wall channeling. It also describes aspects of ongoing work aimed at using magnetic configurations in spin ice to manipulate microwave resonances. The chapter discusses few specific consequences of the interaction, namely the appearance of an underlying drift current in certain geometries and focusing effects such as caustics. It examines exclusively square artificial spin ice (ASI) for which magnetic elements are aligned in few sets of rows on square lattice. The chapter describes a number of recent examples of how relatively simple material designs can produce spin wave phenomena, such as channeled nonreciprocity, that is at once interesting and potentially useful.
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Spin-torque oscillators
J.-V. Kim
in vol. 63 of Solid State Physics, R. L. Stamps and R. E. Camley, eds. (Academic Press, San Diego, 2012), pp. 217-294.
Spin-transfer torques in magnetic heterostructures give rise to a number of dynamical processes that are not accessible with magnetic fields alone. A prominent example involves self-sustained magnetization oscillations, which are made possible through the compensation of magnetic damping by the transfer of spin angular momentum from a spin-polarized current. In this contribution, the theoretical aspects of magnetization oscillations driven by spin torques, such as spin waves and vortex gyration, are presented in detail and key experimental results are highlighted. It is shown how simple but useful models can be derived from fundamental theories of magnetization dynamics and used to describe a variety of stochastic and nonlinear phenomena.
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