Quantitative Ultrafast Magnetoacoustics at Magnetic Metasurfaces

Abstract

Femtosecond (fs) time-resolved magneto-optics is applied to investigate laser-excited ultrafast dynamics of onedimensional nickel gratings on fused silica and silicon substrates for a wide range of periodicities Λ = 400−1500 nm. Multiple surface acoustic modes with frequencies up to a few tens of GHz are generated. Nanoscale acoustic wavelengths Λ/n have been identified as n th -spatial harmonics of Rayleigh surface acoustic wave (SAW) and surface skimming longitudinal wave (SSLW), with acoustic frequencies and lifetimes being in agreement with theoretical calculations. Resonant magnetoelastic excitation of the ferromagnetic resonance (FMR) by SAW's third spatial harmonic, and, most interestingly fingerprints of the parametric resonance at 1/2 SAW frequency have been observed. Numerical solutions of Landau−Lifshitz−Gilbert (LLG) equation magnetoelastically driven by complex polychromatic acoustic fields quantitatively reproduce all resonances at once. Thus, our results provide a solid experimental and theoretical base for a quantitative understanding of ultrafast fs-laser-driven magnetoacoustics and tailoring the magnetic-gratingbased metasurfaces at the nanoscale.

Goos–Hänchen Shift Spatially Resolves Magneto-Optical Kerr Effect Enhancement in Magnetoplasmonic Crystals

“…In comparison with the conventional TMOKE measurements, the maximum values of the spatially resolved TMOKE­( x ) are 2.6 times superior. Our findings can improve the functionality of magnetoplasmonic devices operating as sensors − and light modulators. − The spatially resolved magneto-optical effects associated with the GH shift can also be revealed in a wide range of nanophotonic devices such as magnetophotonic crystals, , plasmonic, , and low-loss all-dielectric metasurfaces. − Moreover, the observation of the GH shift can additionally boost the nonlinear magneto-optical, − ultrafast magnetoplasmonic, − and magnetoacoustic effects. , …”

Ultrafast magnetoacoustics in Galfenol nanostructures

“…Subsequent experiments with Ni films demonstrated the excitation of coherent magnons by coherent phonons generated directly in a ferromagnetic material [13] . This work defined a new research field, which was developed experimentally [14] , [15] , [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] and theoretically [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] over the next decade.…”

“…The range of materials studied by ultrafast magnetoacoustic experiments is not so wide. It includes the well-studied Ni [13] , [16] , [17] , [18] , [25] , Yttrium-Iron Garnets (YIG) [19] , [20] , [21] , alloys like (Ga,Mn)As [10] , [11] and Terfenol-D [23] , and multilayer structures [22] . The present review focuses on ultrafast magnetoacoustic experiments with epitaxial films of the metallic ferromagnetic alloy of Iron and Gallium known as Galfenol [49] .…”

Magnon–Phonon Coupling of Synthetic Antiferromagnets in a Surface Acoustic Wave Cavity Resonator

“…Although the material/coupling scheme may differ, the magnitude of g can be compared to other systems. , Finally, according to eq , the coupling strength g is proportional to the square root of the resonance frequency of SAW and magnon (note that V a is proportional to the SAW wavelength, which is inversely proportional to the resonance frequency). It is thus preferable to increase the resonance frequency to obtain systems with large g . , However, one must consider the nontrivial frequency dependence of the phonon and magnon damping to approach the strong coupling regime with a large cooperativity parameter (see eq ). g also scales with the magneto-elastic coupling constant b 1 , which can possibly be engineered by employing thin film heterostructures with unique interface and surface electronic states. , One may also exploit other coupling schemes, such as spin–rotation coupling, which is reported to exhibit a nonlinear frequency dependence …”