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Register a new userUltrafast Time-Resolved Faraday Rotation in EuO Thin Films
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We have investigated the ultrafast spin dynamics in EuO thin films by time-resolved Faraday rotation spectroscopy. The photoinduced magnetization is found to be increased in a transient manner, accompanied with subsequent demagnetization. The dynamical magnetization enhancement showed a maximum slightly below the Curie temperature with prolonged tails toward both lower and higher temperatures and dominates the demagnetization counterpart at 55 K. The magnetization enhancement component decays in ~1 ns. The realization of the transient collective ordering is attributable to the enhancement of the f-d exchange interaction.
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All-optical pump-probe detection of magnetization precession has been performed for ferromagnetic EuO thin films at 10 K. We demonstrate that the circularly-polarized light can be used to control the magnetization precession on an ultrafast time scale. This takes place within the 100 fs duration of a single laser pulse, through combined contribution from two nonthermal photomagnetic effects, i.e., enhancement of the magnetization and an inverse Faraday effect. From the magnetic field dependences of the frequency and the Gilbert damping parameter, the intrinsic Gilbert damping coefficient is evaluated to be {alpha} approx 3times10^-3.
Using a time-resolved magneto-optical Kerr effect (TR-MOKE) microscope, we observed ultrafast demagnetization of inverse-spinel-type NiCo2O4 (NCO) epitaxial thin films of the inverse spinel type ferrimagnet NCO with perpendicular magnetic anisotropy. This microscope uses a pump-probe method, where the sample is pumped at 1030 nm, and magnetic domain images are acquired via MOKE microscopy at 515 nm (the second harmonic). We successfully observed the dynamics of the magnetic domain of the NCO thin film via laser irradiation, and obtained a demagnetization time constant of approximately 0.4 ps. This time constant was significantly smaller than the large time constants reported for other half-metallic oxides. These results, combined with the results of our x-ray photoemission spectroscopy study, indicate that this NCO thin film is a ferrimagnetic metal whose electronic structure deviates from the theoretically predicted half-metallic one.
Ultra-fast transmission electron microscopy (UTEM) combines sub-picosecond time-resolution with the versatility of TEM spectroscopies. It allows one to study the dynamics of materials properties combining complementary techniques. However, until now, time-resolved cathodoluminescence, which is expected to give access to the optical properties dynamics, was still unavailable in a UTEM. In this paper, we report time-resolved cathodoluminescence measurements in an ultrafast transmission electron microscope. We measured lifetime maps, with a 12 nm spatial resolution and sub-nanoseconds resolution, of nano-diamonds with a high density of NV center. This study paves the way to new applications of UTEM and to correlative studies of optically active nanostructures.
We report proximity effects of spin-orbit coupling in EuO$_{1-x}$ films capped with a Pt overlayer. Transport measurements suggest that current flows along a conducting channel at the interface between the Pt and EuO. The temperature dependence of the resistivity picks up the critical behaviors of EuO, i.e., the metal-to-insulator transition. We also find an unusual enhancement of the magnetic anisotropy in this structure from its bulk value which results from strong spin-orbit coupling across the Pt/EuO interface.
Faraday rotation in a magnetoactive medium with time dependent dielectric permittivity tensor is analyzed through both its diagonal and non-diagonal elements. Continuous and pulse incident laser field cases are considered. In a continuous case linear increasing of Faraday rotation angle with time is obtained.In the continuous laser field case Faraday angle of rotation in both time dependent diagonal and non-diagonal element cases shows an increase with periodic oscillations as either positive (time-dependent dielectric permittivity case) or negative (time dependent gyration vector case) and follows a general pattern. Ultrashort pulse can scan the time dependent dielectric permittivity through the Faraday rotation angle.
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