Optical excitation of propagating magnetostatic waves in an epitaxial Galfenol film by an ultrafast magnetic anisotropy change

• Published in: arXiv.org
• Main Authors: Khokhlov, Nikolai E, Gerevenkov, Petr I, Shelukhin, Leonid A, Azovtsev, Andrei V, Pertsev, Nikolay A, Wang, Mu, Rushforth, Andrew W, Scherbakov, Alexey V, Kalashnikova, Alexandra M
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 20.08.2019
• Subjects: Anisotropy; Crystallography; Epitaxial growth; Excitation; Ferromagnetic materials; Ferrous alloys; Galfenol; Gallium base alloys; Lasers; Magnetic alloys; Magnetic anisotropy; Magnons; Optical microscopy; Physics - Mesoscale and Nanoscale Physics; Physics - Strongly Correlated Electrons; Propagation; Substrates; Surface waves; Wave propagation
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1904.05171

Using a time-resolved optically-pumped scanning optical microscopy technique we demonstrate the laser-driven excitation and propagation of spin waves in a 20-nm film of a ferromagnetic metallic alloy Galfenol epitaxially grown on a GaAs substrate. In contrast to previous all-optical studies of spin waves we employ laser-induced thermal changes of magnetocrystalline anisotropy as an excitation mechanism. A tightly focused 70-fs laser pulse excites packets of magnetostatic surface waves with a \(e^{-1}\) propagation length of 3.4 \(\mu\)m, which is comparable with that of permalloy. As a result, laser-driven magnetostatic spin waves are clearly detectable at distances up to 10 \(\mu\)m, which promotes epitaxial Galfenol films to the limited family of materials suitable for magnonic devices. A pronounced in-plane magnetocrystalline anisotropy of the Galfenol film offers an additional degree of freedom for manipulating the spin waves' parameters. Reorientation of an in-plane external magnetic field relative to the crystallographic axes of the sample tunes the frequency, amplitude and propagation length of the excited waves.