Enhancing the spin transfer torque in magnetic tunnel junctions by ac modulation

Abstract

The phenomenon of spin transfer torque (STT) has attracted a great deal of interests due to its promising prospects in practical spintronic devices. In this paper, we report a theoretical investigation of STT in a noncollinear magnetic tunnel junction under ac modulation based on the nonequilibrium Green's function formalism, and derive a closed-formulation for predicting the time-averaged STT. Using this formulation, the ac STT of a carbon-nanotube-based magnetic tunnel junction is analyzed. Under ac modulation, the low-bias linear (quadratic) dependence of the in-plane (out-of-plane) torque on bias still holds, and the $\sin \theta$ dependence on the noncollinear angle is maintained. By photon-assisted tunneling, the bias-induced components of the in-plane and out-of-plane torques can be enhanced significantly, about 12 and 75 times, respectively. Our analysis reveals the condition for achieving optimized STT enhancement and suggests that ac modulation is a very effective way for electrical manipulation of STT.

arXiv comment23 pages, 5 figures

References in corpus (19)

• Time-dependent transport in interacting and non-interacting mesoscopic systems
• Current-driven Magnetization Reversal and Spin Wave Excitations in Co/Cu/Co Pillars
• Spin Transfer Torques
• Anatomy of Spin-Transfer Torque
• Measurement of the Spin-Transfer-Torque Vector in Magnetic Tunnel Junctions
• Evidence for reversible control of magnetization in a ferromagnetic material via spin-orbit magnetic field
• Thermal Spin-Transfer Torques in Magnetoelectronic Devices
• Anomalous Bias Dependence of Spin Torque in Magnetic Tunnel Junctions
• Carbon Nanotube Based Magnetic Tunnel Junctions
• Ab initio studies of the spin-transfer torque in tunnel junctions
• Current-driven ferromagnetic resonance, mechanical torques and rotary motion in magnetic nanostructures
• Nanoscale Magnetic Heat Pumps and Engines
• Current-induced spin torque resonance of a magnetic insulator
• Current Induced Order Parameter Dynamics: Microscopic Theory Applied to Co/Cu/Co spin valves
• Nonlinear bias dependence of spin-transfer torque from atomic first principles
• Permalloy-based carbon nanotube spin-valve
• Time-Dependent Spintronic Transport and Current-Induced Spin Transfer Torque in Magnetic Tunnel Junctions
• Comparison between thermal and current driven spin-transfer torque in nanopillar metallic spin valves
• Shot noise of spin current and spin transfer torque

Cited by in corpus (3)

• Thermal engineering in low-dimensional quantum devices: a tutorial review of nonequilibrium Green's function methods
• Controlled spin-torque driven domain wall motion using staggered magnetic nanowires
• Transient spin current under a thermal switch