Fig. 5
From: Towards magnonic devices based on voltage-controlled magnetic anisotropy
Excitation of coherent propagating spin waves (SWs). Schematic diagrams show SW excitation by various means. a When radio frequency (rf) current is sent through a microwave antenna, the generated Oersted field inductively couples to the SWs having same frequency (ω) as the rf current. The wavelengths of the SWs are decided by the periodicity of nonuniform Oersted field. b When an unpolarized current is sent through a ferromagnetic layer (fixed layer), the current is spin-polarized due to the exchange interaction of moving electron spins with the localized magnetic spins in ferromagnet. If this spin-polarized current enters into a second ferromagnetic layer (free layer) through a nanocontact, it locally introduces a torque (known as spin-transfer torque) into the magnetic moments and excites SWs, which can propagate along the ferromagnetic layer13. Reprinted by permission from Springer Nature: Nature Nanotechnology, Direct observation of a propagating spin wave induced by spin-transfer torque., Madami, M., Bonetti, S., Consolo, G., Tacchi, S., Carlotti, G., Gubbiotti, G., Mancoff, F. B., Yar, M. A., Akerman, J., copyright 2011. c Femtosecond laser pulses can partially or fully demagnetize an ordered magnetic material within sub-picosecond time scale and efficiently excite coherent propagating SWs15 (licensed under CC BY 4.0). d If the interfacial perpendicular magnetic anisotropy (iPMA) of an ultrathin ferromagnetic film is locally modulated by applying a microwave voltage across a metal gate electrode and waveguide, propagating SWs are excited when frequency of microwave voltage equals to the SW frequency1. e Decay of SW amplitude with propagation distance excited by voltage-controlled magnetic anisotropy (VCMA) and microwave antenna. Reprinted from Rana, B., Fukuma, Y., Miura, K., Takahashi, H. & Otani, Y. Excitation of coherent propagating SWs in ultrathin CoFeB film by voltage-controlled magnetic anisotropy, Appl. Phys. Lett. 111, 052404 (2017), with the permission of AIP Publishing. f Linear variation of VCMA-induced SW amplitude with radio frequency voltage (Vrf)1. Reprinted from Rana, B., Fukuma, Y., Miura, K., Takahashi, H. & Otani, Y. Excitation of coherent propagating SWs in ultrathin CoFeB film by voltage-controlled magnetic anisotropy, Appl. Phys. Lett. 111, 052404 (2017), with the permission of AIP Publishing
