Shun Kanai 교수

The electric field-induced ∼180° magnetization reversal is realized for a sputtered CoFeB/MgO-based magnetic tunnel junction with perpendicular magnetic easy axis in a static external magnetic field. Application of bias voltage with nanoseconds duration results in a temporal change of magnetic easy axis in the free layer CoFeB to in-plane, which induces precessional motion of magnetization in the free layer. The magnetization reversal takes place when the bias voltage pulse duration is adjusted

We propose and demonstrate a scheme for magnetization switching in magnetic tunnel junctions, in which two successive voltage pulses are applied to utilize both spin-transfer torque and electric field effect. Under this switching scheme, a CoFeB/MgO magnetic tunnel junction with perpendicular magnetic easy axis is shown to switch faster than by spin-transfer torque alone and more reliably than that by electric fields alone.

Accompanying data for the main text and supplemental materials of <strong><em>Generalized scaling of spin qubit coherence in over 12,000 host materials</em></strong>

We show the electric-field induced magnetization switching for CoFeB/MgO magnetic tunnel junctions with thick MgO barrier layer of 2.8 nm, whose resistance-area product is 176 kΩ μm2, and achieve the small switching energy of 6.3 fJ/bit. The increase of the junction resistance is expected to suppress the energy consumption due to the Joule heating during the switching; however, the energy is still dominated by the Joule energy rather than the charging energy. This is because the junction resista

Electric field-induced magnetization switching through magnetization precession is investigated as a function of in-plane component of external magnetic field for a CoFeB/MgO-based magnetic tunnel junction with perpendicular easy axis. The switching probability is an oscillatory function of the duration of voltage pulses and its magnitude and period depend on the magnitude of in-plane magnetic field. Experimental results are compared with simulated ones by using Landau-Lifshitz-Gilbert-Langevin

We measure homodyne-detected ferromagnetic resonance (FMR) induced by the electric-field effect in a CoFeB/MgO/CoFeB magnetic tunnel junction (MTJ) with perpendicular magnetic easy axis under dc bias voltages up to 0.1 V. From the bias dependence of the resonant frequency, we find that the first order perpendicular magnetic anisotropy is modulated by the applied electric field, whereas the second order component is virtually independent of the electric field. The lineshapes of the FMR spectra ar

Reducing the relaxation time between binary spin states is crucial to enhance the speed and accuracy of a spintronics-based approach for a probabilistic computer, as envisioned by R.P. Feynman. Contrary to previous perception that the reduction of the energy barrier between the states is the most efficient way, the authors discover here that the relaxation time in in-plane easy-axis nanomagnets is widely controllable by changing the effective perpendicular anisotropy field, even though it has no

We study the spin and orbital magnetic moments in Ta/Co0.4Fe0.4B0.2/MgO by x-ray magnetic circular dichroism measurements as well as first-principles calculations, in order to clarify the origin of the perpendicular magnetic anisotropy. Both experimental and theoretical results show that orbital magnetic moment of Fe is more anisotropic than that of Co with respect to the magnetization direction. The anisotropy is larger for thinner CoFeB, indicating that Fe atoms at the interface with MgO contr

We investigate the physical mechanism governing the sigmoid-like time-averaged response of stochastic magnetic tunnel junctions (s-MTJ), which is a promising building block for probabilistic computers. We measure the time-averaged resistance of perpendicular easy-axis s-MTJs with various free-layer thicknesses and diameters as functions of an external magnetic field and current. The time-averaged response shows no significant dependence on the free-layer thickness, whereas significantly varies w

We investigate the magnetic anisotropy in as-deposited and annealed Ta/ CoFeB/ MgO samples prepared by sputtering and its CoFeB thickness dependence. The magnetic easy axis changes from in-plane to perpendicular with decreasing CoFeB thickness. The thickness, at which magnetic easy axis direction changes, is increased by annealing. It is also shown that the magnetic anisotropy can be modulated by electric field and its modulation ratio is larger for the annealed samples.

We investigate the write-error rate (WER) of spin-transfer torque (STT)-induced switching in nanoscale magnetic tunnel junctions (MTJs) for various pulse durations down to 3 ns. While the pulse duration dependence of switching current density shows a typical behavior of the precessional regime, WER vs current density is not described by an analytical solution known for the precessional regime. The measurement of WER as a function of magnetic field suggests that the WER is characterized by an eff