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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

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We investigated laser-pulse-induced terahertz (THz) emission in Ta/CoFeB/Ir/CoFeB/Ta layered synthetic magnets with different Ir spacer thicknesses. THz emissions were observed under no applied magnetic fields for samples exhibiting interlayer antiferromagnetic exchange couplings, and those THz emissions also showed oscillatory behavior against the Ir spacer thicknesses. These results are qualitatively explained with the THz emission mechanism due to the inverse spin Hall effect for the laser-induced spin current in the layered structures. We also discuss the effect of a non-collinear configuration of magnetizations on THz emission with macrospin simulation.