Publications by Author

Dr. Ilya Krivorotov

Nanowire Spin Torque Oscillator Driven by Spin Orbit Torques

Published in: Nature Communications 5, Article number: 5616 (2014)

Description: Spin torque from spin current applied to a nanoscale region of a ferromagnet can act as negative magnetic damping and thereby excite self-oscillations of its magnetization. In contrast, spin torque uniformly applied to the magnetization of an extended ferromagnetic film does not generate self-oscillatory magnetic dynamics but leads to reduction of the saturation magnetization. Here we report studies of the effect of spin torque on a system of intermediate dimensionality—a ferromagnetic nanowire. We observe coherent self-oscillations of magnetization in a ferromagnetic nanowire serving as the active region of a spin torque oscillator driven by spin orbit torques. Our work demonstrates that magnetization self-oscillations can be excited in a one-dimensional magnetic system and that dimensions of the active region of spin torque oscillators can be extended beyond the nanometre length scale.

Spin Orbit Torques

Dr. Mingzhong Wu

Generation of pure spin currents via spin Seebeck effect in self-biased hexagonal ferrite thin films

Published in: Applied Physics Letter 105, 242412 (2014)

Light-induced generation of pure spin currents in a Pt(2.5 nm)/BaFe12O19(1.2 lm) /sapphire(0.5 mm) structure is reported. The BaFe12O19 film had strong in-plane uniaxial anisotropy and was therefore self-biased. Upon exposure to light, a temperature difference (DT) was established across the BaFe12O19 thickness that gave rise to a pure spin current in the Pt via the spin Seebeck effect. Via the inverse spin Hall effect, the spin current produced an electric voltage across one of the Pt lateral dimensions. The voltage varied with time in the same manner as DT and flipped its sign when the magnetization in BaFe12O19 was reversed.

Spin Currents

Dr. Tingyong Chen

Control of thermal gradient using thermoelectric coolers for study of thermal effects

Published in: Journal of Applied Physics 117, 17C508 (2015)

Thermoelectric coolers based on the Peltier effect have been utilized to control temperature gradient to study thermal effects in both bulk and thin film samples. The temperature gradient is controlled by two coolers and the polarity of the thermal gradient can be reversed by reversing an electric driven voltage. With appropriate controlled thermal gradient using this technique, the Nernst and the Seebeck effects can be measured in both bulk and thin film samples free of spurious contributions. In an arbitrary direction of thermal gradient, the Seebeck and the Nernst components can be decomposed from the measured signal based on the symmetry of the effects in a magnetic field.

Control of thermal gradient