Optical Frequency Up-Conversion of the Ferromagnetic Resonance in an Ultrathin Garnet Mediated by Magnetoelastic Coupling

4D visualization of the light-induced coherent magnon by an X-ray free electron laser

“…We remark that the overall fluence dependence in Fig. 4c is in stark contrast with that for the coherent magnon driven by photoinduced strain on lattice 30,32,33,48 . The photoexcitation above and below the band gap are able to produce the strain through one-photon and twophoton absorption processes, respectively.…”

“…We find a remarkable amplification of the photomagnetic effect by the above-band-gap photoexcitation, which exhibits substantial field of 187 mT with the laser fluence of 1.0 mJ/cm 2 in contrast to 12.3 mT for the below-band-gap photoexcitation. This observation underscores a highly energy-efficient route to achieve substantial photoinduced fields desired for optospintronics applications 31 , which has been obscured with other photoinduced strain 30,32,33 or heating effects 4 . The scope of the applications even broadens for multiferroics with magnetic and electric dipoles strongly coupled to each other, with the notion that the optical manipulation of a magnetic moment will be also functional for controlling the ferroelectric polarization, and vice versa 26,34,35 .…”

Spin reorientation transition in CoFeB/MgO/CoFeB tunnel junction enabled by ultrafast laser-induced suppression of perpendicular magnetic anisotropy

“…For comparison, a laser-induced increase of only 20% was recently reported for the precession frequency in a ferrimagnetic garnet film subjected to pump fluences at least 10 times larger than those used in our experiments. 50 We believe that the revealed optical suppression of PMA and the laser-driven ultrafast SRT in CoFeB/MgO nanostructures have useful prospective implementations. First, such SRT renders it possible to realize ultrafast resistive switching in a CoFeB/MgO/CoFeB tunnel junction, which corresponds to the transformation of a non-collinear magnetic state into a collinear one or vice versa.…”

“…3a and b provide a unique possibility for both qualitative and quantitative evaluation of the laser-induced variation of magnetic anisotropy. 49,50 Indeed, the precession frequency depends not only on the strength and direction of the applied magnetic field but also on the saturation magnetization and magnetic anisotropy. 48 This is evident from the Smit-Suhl formula, which expresses the resonance frequency f of magnetization precession through the second derivatives of the magnetic energy density F m = F an − μ 0 M S m•H ext with respect to the polar angle θ and the azimuth angle φ defining the magnetization direction in the spherical coordinate system.…”

“…For comparison, a laser-induced increase of only 20% was recently reported for the precession frequency in a ferrimagnetic garnet film subjected to pump fluences at least 10 times larger than those used in our experiments. 50…”