Speaker
Description
Magnetic field sensors are essential in our modern-day society, utilized in various applications including automobiles, mobile phones, and robotics. In this talk, I will discuss our work on magnetic field sensors that exploit spin orbit torque (SOT) to detect all three components of an external field with a single device. Initially, the focus will be on sensors where the signal is derived from the anomalous Hall effect. We demonstrate that active offset compensation for all three components is feasible through the SOT effect and a spinning current method applied to the anomalous Hall effect sensors. The SOT effect is induced by a spin-polarized current generated in a heavy metal (HM) layer via an electrical current, which then exerts a torque on a ferromagnetic (FM) layer positioned above the HM layer. This interaction modulates the magnetization of the free layer, enabling an offset-compensated sensor signal. Our results include various free layer designs aimed at achieving sensors with distinct linear regimes. One design utilizes a CoFeB free layer coupled with MgO, where the perpendicular anisotropy at the CoFeB/MgO interface compensates for shape anisotropy, resulting in sensors with linear ranges around 1 mT—ideal for detecting very low field strengths. Another design enhances the linear range using [W/CoFeB/MgO] multilayers. The presentation will conclude with the introduction of the first prototypes of spin orbit torque sensors that employ tunneling magnetic resistance for readout, significantly enhancing sensor sensitivity.
References
[1] S. Koraltan et al., “Skyrmionic device for three dimensional magnetic field sensing enabled by spin-orbit torques.” arXiv, 2024. doi: 10.48550/ARXIV.2403.16725.
