Dynamic coupling of ferromagnets via spin Hall magnetoresistance

Abstract

The synchronized magnetization dynamics in ferromagnets on a nonmagnetic heavy metal caused by the spin Hall effect is investigated theoretically. The direct and inverse spin Hall effects near the ferromagnetic/nonmagnetic interface generate longitudinal and transverse electric currents. The phenomenon is known as the spin Hall magnetoresistance effect, whose magnitude depends on the magnetization direction in the ferromagnet due to the spin transfer effect. When another ferromagnet is placed onto the same nonmagnet, these currents are again converted to the spin current by the spin Hall effect and excite the spin torque to this additional ferromagnet, resulting in the excitation of the coupled motions of the magnetizations. The in-phase or antiphase synchronization of the magnetization oscillations, depending on the value of the Gilbert damping constant and the field-like torque strength, is found in the transverse geometry by solving the Landau-Lifshitz-Gilbert equation numerically. On the other hand, in addition to these synchronizations, the synchronization having a phase difference of a quarter of a period is also found in the longitudinal geometry. The analytical theory clarifying the relation among the current, frequency, and phase difference is also developed, where it is shown that the phase differences observed in the numerical simulations correspond to that giving the fixed points of the energy supplied by the coupling torque.

16 pages, 7 figures, published

References in corpus (10)

• Theory of spin Hall magnetoresistance
• Spin-torque switching: Fokker-Planck rate calculation
• Impact of the electrical connection of N Spin Transfer Oscillators on their synchronization : an analytical study
• Spin torque switching of an in-plane magnetized system in a thermally activated region
• Magnetization reversal condition for a nanomagnet within a rotating magnetic field
• Spin Torque Oscillators with Thermal Noise: A Constant Energy Orbit Approach
• Critical current of spin transfer torque-driven magnetization dynamics in magnetic multilayers
• Magnetoresistance generated from charge-spin conversion by anomalous Hall effect in metallic ferromagnetic/nonmagnetic bilayers
• Nonlinear analysis of magnetization dynamics excited by spin Hall effect
• Linewidth of Power Spectrum Originated from Thermal Noise in Spin Torque Oscillator

Cited by in corpus (5)

• Mutual synchronization of spin-torque oscillators consisting of perpendicularly magnetized free layers and in-plane magnetized pinned layers
• Synchronized, periodic, and chaotic dynamics in spin torque oscillator with two free layers
• Out-of-plane magnetization oscillation in spin Hall device assisted by field-like torque
• Feedback voltage driven chaos in a three-terminal spin-torque oscillator
• Coupled dynamics of magnetizations in spin-Hall oscillators via spin current injection