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Control of magnetism has been an attracting issue due to its scientific interests and technological application. In such research, theoretical simulation plays an important role. We performed a Landau-Lifshitz-Gilbert simulation on the recovery process of a ferromagnet from a magnetization reversed state in a square lattice system. During the process, there can be a situation that the magnetization reversal state is enhanced or completed transiently, which may be observed experimentally.

The core-level resonant magneto-optical Kerr effect of a ferrimagnetic metal alloy, Gd23Fe67Co10, was measured at the Fe M-shell and Gd N-shell absorption edges using rotating analyzer ellipsometry. The large Kerr rotation angle of several degrees was detected at room temperature. The signal was found to be large enough for element-selective magneto-optical experiments to trace the various magnetic events, such as all-optical magnetization switching.

We present an approach to selectively examine an asymmetric potential in the buried layer of solar cell devices by means of nonlinear x-ray spectroscopy. Detecting second harmonic generation signals while resonant to the SiO2 core level, we directly observe existence of the band bending effect in the SiO2 nanolayer, buried in the heterostructures of Al/LiF/SiO2/Si, TiO2/SiO2/Si, and Al2O3/SiO2/Si. The results demonstrate high sensitivity of the method to the asymmetric potential that determines performance of functional materials for photovoltaics or other optoelectronic devices.

Strong spin‐charge interactions in several ferromagnets are expected to lead to subpicosecond (sub‐ps) magnetization of the magnetic materials through control of the carrier characteristics via electrical means, which is essential for ultrafast spin‐based electronic devices. Thus far, ultrafast control of magnetization has been realized by optically pumping a large number of carriers into the d or f orbitals of a ferromagnet; however, it is extremely challenging to implement by electrical gating. This work demonstrates a new method for sub‐ps magnetization manipulation called wavefunction engineering, in which only the spatial distribution (wavefunction) of s (or p) electrons is controlled and no change is required in the total carrier density. Using a ferromagnetic semiconductor (FMS) (In,Fe)As quantum well (QW), instant enhancement, as fast as 600 fs, of the magnetization is observed upon irradiating a femtosecond (fs) laser pulse. Theoretical analysis shows that the instant enhancement of the magnetization is induced when the 2D electron wavefunctions (WFs) in the FMS QW are rapidly moved by a photo‐Dember electric field formed by an asymmetric distribution of the photocarriers. Because this WF engineering method can be equivalently implemented by applying a gate electric field, these results open a new way to realize ultrafast magnetic storage and spin‐based information processing in present electronic systems.