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We report on the dynamics of laser-induced magnetization in magnetic ribbons using the time-resolved magneto-optical Kerr effect. Damped oscillations representing precessional motion of the magnetization vector are observed in a $\mathrm{Co}$-rich ribbon. The frequency and amplitude of these oscillations depend on the fluence of the pump laser pulse and the external magnetic field. With an anisotropy factor defined by the effective field of the magnetic anisotropy, we demonstrate that the frequency of the ferromagnetic mode activated by the laser pulses is close to the frequency of the giant magnetoimpedance response. These findings provide an opportunity to investigate the magnetoimpedance effect in the gigahertz frequency range using ultrashort laser pulses and are particularly interesting for the development of broadband sensor devices. Furthermore, our results link laser-induced magnetization dynamics with magnetoresistive sensing techniques, thus opening up the supergigahertz domain to magnetoimpedance studies.

We report a strong angular asymmetry of optical second-harmonic generation (SHG) in plasmonic crystals formed by an Au grating on top of an anisotropic bismuth-thulium iron garnet (BTIG) film. We found that a weak anisotropy-driven angular SHG asymmetry of the crystalline BTIG is resonantly enhanced and reaches 95% as the surface plasmon polariton (SPP) is excited at the Au/BTIG interface. The asymmetry introduced by an interference of the odd and even (with respect to the angle of incidence) SHG fields is attributed to the anisotropy of the BTIG film. The angular SHG spectra are reproduced using a simple model with a resonant SPP-induced SHG contribution from the anisotropic Au/BTIG interface. The observed asymmetry of the SHG provides valuable insight into the mechanisms of nonlinear plasmonics and can noticeably expand its abilities regarding active light conversion and manipulation.

The ultrafast laser-induced response of spins and charges in $\mathrm{CoFe}/{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ multilayers are studied using THz and optical pump-probe spectroscopies. We demonstrate the possibility of ultrafast manipulation of the transport and magnetic properties of the multilayers with femtosecond laser excitation. In particular, using time-resolved THz transmission experiments we found that such an excitation leads to a rapid increase of the THz transmission (i.e., electric resistivity). Our experiments also reveal that femtosecond laser excitation results in the emission of broadband THz radiation. To reveal the origin of the emitted THz radiation, we performed magnetic-dependent measurements of the THz emission. We also compared the observed electric field of the THz radiation to calculations performed using subpicosecond laser-induced demagnetization measurements. The good agreement between the experimentally obtained spectra and the calculations corroborates that the measured THz emission originates from the demagnetization process.

Using pump-probe optical polarimetry we demonstrate that femtosecond laser excitation of a 2D regular lattice of magnetic nanodots effectively changes the optical anisotropy of the array. Study of the dynamics of the femtosecond laser-induced anisotropy reveals four main mechanisms occurring in the electronic, spin, and lattice subsystems. Below 1 ps, a strong Kerr-like nonlinearity causes linear birefringence, with its axis directed along the electric field of the linearly polarized femtosecond laser pump pulse. In addition, a long-living linear birefringence is also induced due to slowly relaxing excitations. Also below 1 ps, ultrafast laser-induced demagnetization of Co leads to a partial breakdown of the circular birefringence of the magnetic nanodots. On the timescale up to 300 ps, optically triggered acoustic modes of the dots drive oscillations of the linear optical birefringence. During this process, the oscillations damp while transferring their energy into acoustic modes of the substrate. On the nanosecond timescale, the signal is dominated by acoustic oscillations at the surface of the substrate.

Laser-induced ultrafast demagnetization in ferrimagnetic Gd${}_{x}$Fe${}_{100\ensuremath{-}x\ensuremath{-}y}$Co${}_{y}$ thin films was studied experimentally as a function of Gd concentration ($x=18$, 22, 24, 30%, and $y\ensuremath{\approx}9$--10%), pump fluence, and sample temperature. The results showed that the conditions for full demagnetization at the ultrafast time scale in Gd${}_{x}$Fe${}_{100\ensuremath{-}x\ensuremath{-}y}$Co${}_{y}$ thin metal films are easily achieved below the magnetization compensation point (${T}_{M}$) and, furthermore, when the ratio between Gd and Fe concentrations is not too large. Consequently, the ultrafast demagnetization strongly depends on the initial temperature of these alloys compared to their ${T}_{M}$. These results provide further insight into the unconventional ultrafast dynamics of multisublattice metallic magnets.

Hot carrier-induced spin dynamics is analyzed in epitaxial Au=Fe=MgOð001Þ by a time domain approach. We excite a spin current pulse in Fe by 35 fs laser pulses. The transient spin polarization, which is probed at the Au surface by optical second harmonic generation, changes its sign after a few hundred femtoseconds. This is explained by a competition of ballistic and diffusive propagation considering energy-dependent hot carrier relaxation rates. In addition, we observe the decay of the spin polarization within 1 ps, which is associated with the hot carrier spin relaxation time in Au.