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Skyrmion is a topologically stable spin texture and expected to be applied to the future computer memory. On the semiconductors such as FeGe and MnSi, the skyrmion configuration is stable in the sense that it is not strongly affected by a small variation of external stimuli such as temperature, magnetic field etc. In recent experiments, it was reported that the skymion shape is deformed from isotropic (or circular shape) to anisotropic (or elliptic shape) by an external mechanical stress. This shape deformation is caused by the so-called “strain-induced anisotropy (SIA)” of Dzyaloshinskii-Moriya interaction (DMI). In this presentation, we study the reason why this SIA appears in the DMI coefficient on the basis of Finsler geometry modeling technique by introducing a microscopic strain field τ, which is caused by or interacts with the applied external mechanical force.

Skyrmions are topologically stable and energetically balanced spin configurations appearing under the presence of ferromagnetic interaction (FMI) and Dzyaloshinskii-Moriya interaction (DMI).Much of the current interest has focused on the effects of magneto-elastic coupling (MEC) on these interactions under mechanical stimuli, such as uniaxial stresses for future applications in spintronics devices. Recent studies suggest that skyrmion shape deformations in thin films are attributed to an anisotropy in the coefficient of DMI, such that D x = D y . This anisotropy is naturally understood as an effect of MEC, however, the relationship between MEC and anisotropy in DMI remains to be clarified. In this paper, we study this problem using a new modeling technique constructed based on Finsler geometry (FG). In the FG model, an MEC is implemented purely geometrically, and the implemented MEC dynamically deforms the coefficients of FMI and DMI to be direction-dependent. This modeling technique is in sharp contrast to the standard model of MEC, in which anisotropic constants are explicitly assumed as an input parameter. Two possible FG models are examined: In the first (second) model, the FG modeling prescription is applied to the FMI (DMI) Hamiltonian. We find that these two different FG models' results are consistent with the reported experimental data for skyrmion deformation. We also study responses of spins under lattice deformations corresponding to uniaxial extension/compression and find a clear difference between these two models in the stripe phase, elucidating which interaction of FMI and DMI is deformed to be anisotropic by uniaxial stresses.

A new technique for rapidly discriminating shapes and/or sizes of micrometre size particles which are spatially distributed on a large scale has been developed. The technique is based on multiplexed matched spatial filtering, which is a kind of Fourier holographic filtering technique. Using the technique, large view visualization of the spatial distribution and the spatial behaviour of specific particles (e.g. aerosols, allergen particles, red blood cells, etc) can be realized. To make the multiplexed matched spatial filter (MMSF), a new material for hologram recording has been applied. The material is a photoconductor plastic which is processed by a solvent vapour and a corona discharge. The method of hologram recording is a dry process, which processes the material in several minutes at the initial settings of the device. Therefore, the MMSF can be made very easily in a short time. In the research, the discrimination of spatial behaviour of moving particles of different shape and/or size has been carried out by the MMSF made by the photoconductor plastic material.

Using the recently discovered phenomenon of photoenhanced magnetization in GaAs–Fe semiconductor-ferromagnet composite films [S. Haneda, S. Koshihara, and H. Munekata, Physica E 10, 437 (2001)], we have demonstrated a light-driven microactuator. It consists of a GaAs–Fe/GaAs(100) chip glued onto a 4.3 mm long, 2.1-μm-thick Si cantilever. A deflection of 0.7 μm was achieved when the cantilever was illuminated with 650 nm, 713 μW laser light in a magnetic field of 1.7 T at room temperature.

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We report simulation results of skyrmions on fluctuating 2D lattices, where the vertices r i (∈ R 3 ) are treated as a dynamical variable and, hence, there is no crystalline structure. On the fluctuating surfaces, an external magnetic field perpendicular to the surface, Dzyaloshinskii-Moriya and ferromagnetic interactions are assumed in addition to the Helfrich-Polyakov Hamiltonian for membranes. The surface (or frame) tension τ is calculated under both isotropic and uniaxial strain conditions, and this calculation clarifies a nontrivial dependence of τ on the skyrmion, stripe, and ferromagnetic phases. We find that the variation of τ with respect to the applied magnetic field in the skyrmion phase is accompanied by a variation of the total number of skyrmions. Moreover, we find that this total number variation is qualitatively consistent with a recent experimental result for the creation/annihilation of skyrmions of 3D crystalline material under uniaxial stress conditions. It is also found that the stripe phase is significantly influenced by uniaxial strains, while the skyrmion phase remains unchanged. These results allow us to conclude that the skyrmion phase is stable even on fluctuating surfaces.