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(a) Resistivity of our sputtered W films as a function of thickness. The films are capped by CoFeB and the CoFeB conductance is subtracted. (b) X-ray diffraction patterns for sputtered W(8 nm) (upper blue trace line) and W(6 nm) (lower red trace line) films (without a CoFeB cap). The arrows indicate the identifications of the Bragg peaks and the corresponding diffraction planes.
(a) Schematic illustration of the ST-FMR device and the circuit layout for measurements of the resonance linewidth versus DC current. (b) The change of the effective damping constant as a function of DC current charge density for two angles of applied magnetic field. The RF frequency f = 9 GHz. The solid lines represent fits to Eq. (1).
(a) Schematic illustration of the β-W 3-terminal device and the measurement circuit layout. (b) Differential resistance (dV/dI) minor loop for the MTJ without any DC current along the β-W bottom channel. The measured resistance includes a 2 kΩ lead resistance from the W channel that is not subtracted here. The external magnetic field was applied along the long axis of the nano-pillar MTJ.
(a) Differential resistance of the MTJ as a function of the DC bias current , exhibiting magnetization switching by the spin Hall torque. An in-plane external magnetic field was applied to cancel the dipole field from the fixed layer. (b) Switching currents as a function of the current ramp rate. The blue squares represent switching currents from the AP to P state, and the red triangles represent switching currents from P to AP. Solid lines are fits to a thermally assisted spin torque switching model.
The spin Hall angle of W as determined from the critical currents for magnetization switching in 3-terminal ST devices.
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