Abstract
A theoretical treatise is presented on coupled dynamics between spin torque oscillators consisting of perpendicularly magnetized free layers and in-plane magnetized pinned layers. As a coupling mechanism, an injection of pure spin current from one oscillator to the other is considered because the free layer is capable of emitting the pure spin current by spin pumping effect. The numerical simulation of the Landau-Lifshitz-Gilbert equation indicates that an in-phase synchronization is excited in the oscillators for a wide range of applied current. The results indicate that injection of the spin current by spin pumping is the efficient approach for an enhancement of emission power in spintronics devices using an array of spin torque oscillators.
Highlights
Coupled motion of magnetizations, such as mutual synchronization of spin torque oscillators (STOs),1–12 is an exciting topic in the field of spintronics from the view points of both fundamental science13,14 and practical applications.15–18 The mechanism of the coupling is magnetic and/or electric interactions between the ferromagnets
Either in-phase or antiphase synchronization, depending on the current magnitude, was found in STOs consisting of in-plane magnetized free layer and perpendicularly magnetized pinned layer coupled via spin pumping
A theoretical study was made on a coupled dynamics between STOs consisting of perpendicularly magnetized free layers and in-plane magnetized pinned layers, where two STOs are connected by a nonmagnetic material
Summary
Coupled motion of magnetizations, such as mutual synchronization of spin torque oscillators (STOs), is an exciting topic in the field of spintronics from the view points of both fundamental science and practical applications. The mechanism of the coupling is magnetic and/or electric interactions between the ferromagnets. The role of spin pumping on FMR in a ferromagnetic multilayer has been extensively studied, the work on the coupled magnetization dynamics in STOs via spin pumping is limited.. We investigate a coupled motion of STOs via spin pumping consisting of perpendicularly magnetized free layers and in-plane magnetized pinned layers. This type of STO has been an interesting research target for high frequency spintronics because it shows a large emission power, narrow linewidth, and wide range tunability of the frequency.. Considering two STOs connected by a nonmagnetic electrode, pure spin current emitted from one STO to the other via spin pumping leads to a coupled motion of the magnetizations.
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