Quantification of a propagating spin-wave packet created by an ultrashort laser pulse in a thin film of a magnetic metal

Abstract

Coherent spin-wave generation by focused ultrashort laser pulse irradiation was investigated for a permalloy thin film at micrometer scale using an all-optical space and time-resolved magneto-optical Kerr effect. The spin-wave packet propagating perpendicular to magnetization direction was clearly observed, however that propagating parallel to the magnetization direction was not observed. The propagation length, group velocity, center frequency, and packet-width of the observed spin-wave packet were evaluated and quantitatively explained in terms of the propagation of a magnetostatic spin-wave driven by ultrafast change of an out-of-plane demagnetization field induced by the focused-pulse laser.Information processing by spin-waves such as spin-wave logic gates or magnon transistors [1][2][3][4][5], has attracted much attention for the realization of future devices with low power consumption. In previous studies, the propagating spin-waves have been excited by a local radiofrequency (rf) magnetic field generated by an rf electric current fed into an antenna [6][7][8][9][10][11][12][13] or by a dc electric current via a spin-transfer-torque [14,15]. Among them, manipulation of spin-waves propagating in thin films of magnetic metals are of interest [6,[8][9][10][11][12], because magnetic metal thin films may be well-suited for integration into silicon nano-technology [16]. However, the propagation length of spin-waves in thin films of magnetic metals is very short, so that the precise characterization of the spin-wave propagation in the near sub-micrometer region is a technological challenge, for which it may be valuable to explore the various observational methods.Recently, it has been demonstrated that a propagating spin-wave can be generated by a

Optical control of magnetization dynamics in Gd–Fe–Co films with different compositions

“…18, which reported monotonic magnetization reversal even in Gd22% samples, we confirmed that the magnetization response of the sample depends not only on the T A value of its Gd-Fe-Co layer, but also on its multilayer structure. Although the quasi-spinwaves observed in our experiments may not qualify as coherent magnons, [9][10][11][12] we achieved an unprecedentedly large precession angle of the induced waves (on the order of 10°). Considering that low-frequency precession is allowed within the uncertainty of our present experiment, and knowing that anomalous behavior occurs in samples with specific heat conduction, experimental and theoretical searches for spin-phonon coupling 19,20) may also be worthwhile.…”

“…7,8) However, the responses of materials to laser pulses are not limited to magnetization switching. The electric and magnetic field vectors of laser beams can interact strongly with electrons in materials, generating coherent magnons [9][10][11][12] and plasmons. 13) Laser-triggered superdiffusive spin currents have transiently modified the equilibrium spin populations in specially designed magnetic structures.…”

Damping of Standing Spin Waves in Bismuth-Substituted Yttrium Iron Garnet as Seen via the Time-Resolved Magneto-Optical Kerr Effect

“…Traditionally, the investigation of SWs and their damping are performed using ferromagnetic resonance (FMR) techniques [6,7]. Alternatively, femtosecond laser pulses have been recently presented as an important tool to trigger SWs in a wide variety of conducting [8][9][10], semiconducting [11][12][13][14][15], and insulating [16][17][18][19][20][21] magnetic materials, as well as probing their real-time dynamics with a very high spatiotemporal resolution using femtosecond magneto-optical pump-probe techniques [22][23][24][25][26]. These highly resolved spatiotemporal investigations provide important opportunities to improve the understanding of SWs, with the aim * madeb@uni-potsdam.de of manipulating their dynamics at the fastest speed and in the most efficient way.…”

Selective Excitation of Localized Spin-Wave Modes by Optically Pumped Surface Acoustic Waves

“…Unfortunately, while propagating spin waves does not require current flow, their excitation, which is typically achieved using optical pulses [4][5][6][7][8] , the Oested field of microwave strip-lines [9][10][11] , or via spin torque effects [12][13][14] , is more problematic. Here, the former approach is limited by the difficulties of miniaturizing powerful laser systems and optics, while the latter two cases inherently require current flow.…”