A square 3-D sensor based on anomalous hall effect and spin hall effect

Magnetic field mapping and three-axis navigation increasingly rely on vector magnetometers that are compact, low-power, and inexpensive. Conventional approaches—based on AMR, Hall, or TMR bridge arrays—often require multiple orthogonal elements, careful trimming, and bulky packaging, which raise cost and introduce inter-axis crosstalk and calibration overhead. Spin–orbit torque (SOT) sensors provide a promising single-die alternative: current-induced torques and harmonic detection enable orthogonal field components to be encoded in different voltage channels without mechanical rotation or complex 3D stacks. This motivates device geometries that are lithography-simple yet functionally three-dimensional, allowing chip-level integration and scalable, low-noise measurement. Such architectures also align with CMOS back-end processing, easing wafer-level production and calibration.

Here, we report a square three-dimensional SOT sensor using a MgO/CoFeB/Ta trilayer. The sensor size is 15×15 μm2 with a 3 μm channel. It detects the out-of-plane field Hz through the first-harmonic anomalous Hall voltage. Damping-like SOT modulates the magnetisation and produces second-harmonic voltages proportional to the in-plane fields Hx and Hy. With a 3 mA, 1 kHz ac drive, the sensor shows sensitivities of 150 μV/Oe for Hz, 2.5 μV/Oe for Hx, and 2.5 μV/Oe for Hy, with good linearity. The simple square geometry minimizes the sensor size. These results show a practical route to high-resolution, low-cost and miniaturized vector magnetic sensing with a single planar device.

Jiaqi Wang is currently a PhD student focus on the area of spintronic material and  device. He received a master degree from National University of Singapore, Singapore and a bachelor degree from Tianjin University, China.