Shoya Sakamoto

Chirality-induced spin selectivity (CISS) is a phenomenon resulting from the interaction between chiral molecules and electron spin. One example is chirality-induced magnetoconductance (MC), in which the electrical conduction through a molecule–ferromagnet junction depends on the molecular chirality and the magnetization direction of the ferromagnet. In this study, we investigate the microscopic mechanism of CISS in an electrochemical cell containing a chiral camphorsulfonic acid electrolyte and a ferromagnetic Ni electrode. We find that the MC effect strongly depends on electrode size, which we attribute to a crossover between one-dimensional planar and three-dimensional radial diffusion. Pronounced MC at large electrodes highlights the importance of the one-dimensional planar diffusion regime. This suggests that magnetization reversal modifies exchange coupling between chiral molecules and the ferromagnet, thereby altering the near-electrode concentration gradient rather than the chemical reaction rate per molecule. These findings identify near-electrode diffusion dynamics as a key factor in CISS-related electrochemical responses.

Artificially‐designed magnetic hetero‐structures with an antiferromagnetic alignment of magnetization in magnetic layers, which exploit the interlayer exchange coupling (IEC) through a non‐magnetic layer, are called synthetic antiferromagnets (SyAF) and are a treasure trove of functionalities for spintronics applications. In SyAF spintronics, a non‐magnetic layer simultaneously providing IEC and large electric current‐induced torque originating from spin‐orbit interaction, called spin‐orbit torque (SOT), has been eagerly desired for efficient magnetization manipulation by current injection. Here we report that amorphous tungsten (W) is a promising non‐magnetic interlayer. Amorphous W shows clear antiferromagnetic coupling at thicknesses from 1.2 to 2.0 nm, which is thicker than other crystallized non‐magnetic interlayers at the first peak thicknesses of IEC oscillation. In addition, the amorphous W generates large SOT based on the intrinsic process of the spin Hall effect, which allows magnetization vector switching in SyAF. Amorphous W does not possess a well‐defined crystal symmetry. Considering this fact, the long‐range IEC and large SOT originating from the electronic structure in amorphous W are counterintuitive findings. The present study revisits what phases are stabilized in thin W layers, and provides a new avenue for utilizing the amorphous phase as a spintronic material.

Phys. Rev. Research 8, 039002 (2026)

Magnetization control in spintronic devices is governed by the Gilbert damping constant, which describes the energy dissipation in magnetization dynamics. Although Gilbert damping is often treated as an isotropic scalar, crystalline symmetry can induce orientational damping anisotropy. This anisotropy is commonly attributed to intraband scattering associated with changes in the electronic density of states, whereas interband scattering has generally been assumed to be isotropic. Here, we show that the anisotropic Gilbert damping of a few atomic layers of Fe in contact with MgO is governed by interband scattering. Time-resolved magneto-optical Kerr measurements reveal that intrinsic damping increases by nearly a factor of 3 when the magnetization tilts from in-plane to out-of-plane. Combined strain-dependent experiments and first-principles calculations identify interband scattering at the Fe/MgO interface as the origin of this effect, providing new insights into magnetization dynamics beyond the conventional intraband-dominated picture.

In this Letter, we study the domain-wall dynamics under electric current in the helimagnet MnAu 2 . We have found that the threshold electric current of the transition from a multidomain state to a single-chiral domain state in a magnetic field is much lower than that of chirality reversal from a single-chiral domain within certain ranges of temperature and magnetic field. The chirality after the transition depends on whether the magnetic field and electric current were parallel or antiparallel. Numerical calculations based on the Landau-Lifshitz-Gilbert equation reproduced the experimental observations. These results indicate that the domain walls are highly mobile in the helimagnet.

Quantitative evaluation of magnetic moment distributions in microstructures with high spatial resolution is essential to advance the development of next-generation spintronic devices. In this study, we successfully imaged the magnetic domain structure of micropatterned subnanometer thin films by combining high-resolution and high-sensitivity imaging using soft x-ray ptychography and x-ray magnetic circular dichroism. Furthermore, by measuring hyperspectral images of magnetic thin-film patterns and applying the sum rule to absorption spectra at each pixel of the image, quantitative two-dimensional measurements of spin and orbital magnetic moments within magnetic domains were achieved. Such measurements provide a powerful evaluation method for the design of devices based on physical phenomena such as spin and orbital currents.