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Hanle magnetoresistance (HMR) is a type of magnetoresistance where interplay of the spin Hall effect, Hanle-type spin precession, and spin-dependent scattering at the top/bottom surfaces in a heavy metal controls the effect. In this study, we modulate HMR in ultrathin Pt by ionic gating, where the surface Rashba field created by a strong electric field at the interface between the ionic gate and Pt plays the dominant role in the modulation. This finding can facilitate investigations of gate-tunable, spin-related effects and fabrication of spin devices.

Iron selenide telluride, FeTeSe, is an attractive layered material for both superconductivity and spintronics applications. FeTeSe enables Ising-type superconductivity, which involves spin-momentum locking. We report superconductivity of mechanically exfoliated thin film FeTe0.6Se0.4that equips ferromagnetic electrodes with perpendicular magnetic anisotropy to detect possible Ising spin paring. The superconducting transition is observed at T= 15 K. More importantly, the upper critical field of FeTe0.6Se0.4is anisotropic and the in-plane upper critical field is measured to be 145 T. These results show that the superconductivity of thin film FeTe0.6Se0.4is robust and FeTe0.6Se0.4can be a potential material stage for super-spintronics.

To augment the magnetoresistance (MR) ratio of n-type non-degenerate Si-based lateral spin valves (Si-LSVs), we modify the doping profile in the Si layer and introduce a larger local strain into the Si channel by changing a capping insulator. The highest MR ratio of 1.4% is achieved in the Si-LSVs through these improvements, with significant roles played by a reduction in the resistance-area product of the ferromagnetic contacts and an enhancement of the momentum relaxation time in the Si channel.

The temperature evolution of a direct-current electromotive force (EMF) generated by spin pumping and the inverse-spin Hall effect in a platinum (Pt)/yttrium iron garnet (YIG) bilayer was investigated down to 80 K. The magnitude of the EMF decreased significantly with decreasing temperature and disappeared at approximately 80 K. 40-nm-thick YIG films fabricated by a metal organic decomposition method exhibited single-peak ferrimagnetic resonance (FMR) spectra without any spin wave resonance, which allowed us to precisely analyze the FMR spectra. We determined that the temperature evolution of the Gilbert damping constant is the dominant factor in the temperature dependence of the EMF. The comparison of the FMR linewidth between the X- and Q-bands revealed that an increase in Gilbert damping constant at low temperatures is not due to the enhancement of the spin pumping efficiency but due to an additional spin relaxation in the YIG film itself, which reduces the precession angle of the magnetization under the FMR conditions.

We experimentally demonstrate a Si spin metal-oxide-semiconductor field-effect transistor (MOSFET) that exhibits a high on/off ratio of source-drain current and spin signals at room temperature. The spin channel is nondegenerate n-type Si, and an effective application of gate voltage in the back-gated structure allows the spin MOSFET operation. This achievement can pave the way for the practical use of the Si spin MOSFET.

The inverse spin Hall effect has made its way from being a peculiar phenomenon predicted and discovered in semiconductors more than 30 years ago to being an extremely important effect in modern spintronics. It allows for the detection and conversion of spin current, along with the probing of the spin-orbit interaction of materials. However, the discrepancy between theoretical and experimental results has slowed down the progress of this branch of spintronics and its applications. In this study, we analyzed yttrium-iron-garnet-based systems highly exploited in spin pumping experiments and demonstrated the correct normalization procedure for the inverse spin Hall effect in such systems.

In this study, the temperature dependence of the spin Hall angle of palladium (Pd) was experimentally investigated by spin pumping. A Ni80Fe20/Pd bilayer thin film was prepared, and a pure spin current was dynamically injected into the Pd layer. This caused the conversion of the spin current to a charge current owing to the inverse spin Hall effect. It was found that the spin Hall angle varies as a function of temperature, whereby the value of the spin Hall angle increases to ca. 0.02 at 133 K.

We demonstrate dynamical spin injection into p-type germanium (Ge) at room temperature (RT) using spin pumping. The generated pure spin current is converted to a charge current by the inverse spin-Hall effect (ISHE) arising in the p-type Ge sample. A clear electromotive force due to the ISHE is detected at RT. The spin-Hall angle for p-type Ge is roughly estimated to be ?SHE= 9.6×10-4at RT.

We report on the first demonstration of generating a spin current and spin transport in a highly doped Si channel at room temperature (RT) using a four-terminal lateral device with a spin injector and a detector consisting of an Fe/MgO tunnel barrier. Spin current was generated using a nonlocal technique, and spin injection signals and Hanle-type spin precession were successfully detected at 300 K, thus proving spin injection with the elimination of spurious signals. The spin diffusion length and its lifetime at RT were estimated to be 0.6 µm and 1.3 ns by the Hanle-type spin precession, respectively.

Auto-oscillation of the magnetization in an Fe/Cr/Fe antiferromagnetically coupled multilayer was induced by spin-transfer torque. The acoustic mode, a coupled mode in the multilayer, was excited when a dc bias current was applied at relatively small magnetic fields. The external magnetic field dependence of the oscillation frequency is explained by a macrospin model with an antiferromagnetic coupling field. The excitation of the optical mode is also discussed.

Microwave-assisted magnetization reversal in a perpendicularly magnetized film was investigated using the anomalous Hall effect. Although the reversal process of the sample in this work was governed by nucleation and domain wall propagation, a large decrease in the reversal field, as much as 75% of the coercive field, was observed when the optimum rf magnetic field was applied. Our results indicate that the microwave-assisted effect promotes nucleation of the reversed domain leading to a reduction of the reversal field in a nucleation-type perpendicularly magnetized system.

The degradation mechanisms of multilayer graphene spin valves are investigated. The spin injection signals in graphene spin valves have been reported to be linearly dependent on the drain bias voltage, which indicates that the spin polarizations of injected spins in graphene are robust with respect to bias voltage. We report that the disappearance of this robustness can be due to two different degradation mechanisms of the spin valves. Our findings indicate that the disappearance of robustness is due to degradation rather than any intrinsic characteristic of graphene. Thus, the robustness can be greatly enhanced if degradation can be prevented.

Growing demands for the voltage-driven spintronic applications with ultralow-power consumption have led to new interest in exploring the voltage-induced magnetization switching in ferromagnetic metals. In this study, we observed a large perpendicular magnetic anisotropy change in Au(001)/ultrathin Fe80Co20(001)/MgO(001)/polyimide/indium tin oxide (ITO) junctions, and succeeded in realizing a clear switching of magnetic easy axis between in-plane and perpendicular directions. Furthermore, employing a perpendicularly magnetized film, voltage-induced magnetization switching in the perpendicular direction under the assistance of magnetic fields was demonstrated. These pioneering results may open a new window of electric-field controlled spintronics devices.

We propose a novel type of "spin transistor", driven by a current-induced magnetic field. The basic structure is composed of a magnetic tunnel junction (MTJ) with low resistance-area product, together with an electrically-isolated metallic wire which can control the magnetization of the free layer of the MTJ by producing a magnetic field. By choosing an optimum cell size, we successfully demonstrated power gain of 5.6. We also found that the current amplification can be realized by reducing the parasitic resistance of the structure. This is the first demonstration of the power amplification in the spintronic device at room temperature.

We observed spin injection into silicon through Fe/MgO tunnel barrier by using non-local magnetoresistance measurement technique. Fe/MgO tunnel barrier contacts with a lateral spin valve structure were fabricated on phosphorus doped silicon-on-insulator substrate. Spin injection signals in the non-local scheme were observed up to 120 K, which is the highest value where band transferred spins in Si have ever been reported, and spin diffusion length was estimated to be about 2.25 µm at 8 K. Temperature dependence and injection current dependence of the non-local voltage were also investigated. It is clarified that MgO tunnel barrier is effective for the spin injection into silicon.

Ink-jet printable thin-film transistors (TFTs) on flexible plastic substrates are an important focus of research because present silicon-based electronics cannot realize such devices. In the present study, we fabricated single-walled carbon nanotube (SWCNT) TFTs on plastic substrates using the ink-jet printing method, and realized high-on/off current ratio (?104) and flexibility, respectively. The present study therefore represents a major step towards "flexible SWCNT electronics".

Real-time measurements of spin-transfer induced magnetization switching were performed at room temperature on elliptical CoFeB/MgO/CoFeB magnetic tunnel junctions (60×170 nm2) using a storage oscilloscope. Free layer thickness and thermal stability factor (KuV/kBT) were 2 nm and 17, respectively. Under small dc current with short rise time (200 ps), the switching processes essentially comprised long waiting time and short transition time (less than 400 ps). We found, for the first time, that switching probability density was considerably lower for few ns after the rise of the current, and became constant later. Existence of this "non-reactive time" could be a critical issue for fast writing applications.