Spin–orbit torque (SOT)-induced perpendicular
magnetization
switching is one of the key solutions for the next generation of magnetic
memory and spin logic applications. Recently, the bulk SOT effect
in a single magnetic layer with a vertical composition gradient has
attracted a lot of attention because it can break through the interfacial
nature of the SOT effect in a traditional bilayer structure. However,
the dependency of the external in-plane magnetic field or the additional
pinning layer for deterministic switching hinders the further application
of this technology. Here, for the first time, we implement field-free
magnetization switching induced by bulk SOT in a single (111)-oriented
CoPt magnetic layer with in-plane remanent magnetization. The initialized
longitudinal in-plane remanent magnetization can substitute the external
magnetic field to break the inversion symmetry and realize continuous
field-free perpendicular magnetization switching. Furthermore, the
in-plane remanent magnetization can be manipulated by the SOT effective
field induced by lateral current pulses, leading to a tunable switching
chirality. A multi-domain micromagnetic model is established to describe
in depth the experimental observations and clarify the relationship
between switching amplitude and easy magnetization cone angle. Our
work provides an alternative solution to realize field-free perpendicular
magnetization switching in a single magnetic layer, which can promote
the development of emerging high-density and low-power SOT-based devices.
Magnetic sensors based on tunneling magnetoresistance (TMR) effect exhibit high sensitivity, small size, and low power consumption. They have gained a lot of attention and have potential applications in various domains.This study first introduces the development history and basic principles of TMR sensors. Then, a comprehensive description of TMR sensors linearization and Wheatstone bridge configuration is presented. Two key performance parameters, the field sensitivity and noise mechanisms, are considered. Finally, the emerging applications of TMR sensors are discussed.
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