Abstract
Spintronic devices often require the ability to locally change the magnetic configuration of ferromagnetic structures on a sub-micron scale. A promising route for achieving this goal is the use of heavy metal/ferromagnetic heterostructures where current flowing through the heavy metal layer generates field-like and anti-damping like torques on the magnetic layer. Commonly, such torques are used to switch magnets with a uniaxial anisotropy between two uniformly magnetized states. Here, we use such torques to switch magnetization in Ta/Ni0.80Fe0.20 heterostructures with uniaxial and biaxial anisotropy, where in the latter the magnetization is non-uniform. The anisotropies are induced by shape and the magnetic state is monitored using the planar Hall effect. As structures with several easy axes induced by shape can be part of a magnetic memory element, the results pave the way for multi-level magnetic memory with spin-orbit torque switching.
Highlights
A common requirement for spintronic devices is an efficient and scalable method to manipulate the magnetic configuration of a ferromagnetic (FM) structure on a sub-micron scale
We monitor the magnetic configuration while generating the spin-orbit torques (SOTs) by using the planar Hall effect (PHE) and we demonstrate the important contribution of the anti-damping torque
As such structures may be one of the magnetic electrodes in magnetic tunnel junctions (MTJs), these results indicate the feasibility of multi-state magnetic memory with SOTs used for write operations
Summary
A common requirement for spintronic devices is an efficient and scalable method to manipulate the magnetic configuration of a ferromagnetic (FM) structure on a sub-micron scale. A flowing charge current in HM/FM heterostructures generates spin-orbit torques (SOTs), owing to the spin Hall effect (SHE) and Rashba effect at the interface, which affect the magnetic layer without injecting a charge current into the FM layer[16,17,18,19,20,21,22] Those effects create two types of torques on the magnetic layer known as field like and an anti-damping like torques. We show field-free current-induced switching in the two types of structures, providing a pathway for practical design of spintronic devices based on bi and multi-easy axes in-plane magnetized heterostructures. As such structures may be one of the magnetic electrodes in MTJs, these results indicate the feasibility of multi-state magnetic memory with SOTs used for write operations
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