Lateral domain wall oscillations in IMA/PMA bilayered nano-strips driven by a perpendicular current: A type of domain wall based oscillators

Abstract

Spin transfer torque-driven dynamic properties of spins in a bilayered nano-strip system composed of a layer with in-plane magnetic anisotropy (IMA) and a layer with perpendicular magnetic anisotropy (PMA) were studied using a micro-magnetic simulation method. It is demonstrated that a domain wall (DW) can nucleate in the IMA layer at the end of the nano-strips and propagate with a large speed toward the other end under a perpendicular current. With DW annihilation and nucleation at either end of the nano-strips, their back and forth motion induces a magnetization oscillation whose amplitude and frequency can be easily manipulated by the current density, the dimensions and material of the nano-strip, and a perpendicularly applied magnetic field. Considering that the oscillation amplitude can be greatly amplified by the simultaneous oscillations of a large number of nano-strips in an array and the simple structure of the each element, this kind of IMA/PMA bilayered nano-strip may have important applications in magnetic nano-oscillators.