We have performed magnetotransport and noise characterization studies of ultrasensitive anomalous Hall effect (AHE) sensors based on the Ta/Co40Fe40B20/MgO multilayer structure. The magnetization is near spin reorientation transition. This greatly reduces the saturation field with improvement of the magnetic sensing performance. We have performed temperature-dependent measurements to investigate the effect of tunable magnetic anisotropy. Both 1/f noise and sensitivity have a strong temperature dependence. Moreover, the scaling relations between 1/f noise and sensitivity change dramatically as temperature changes, showing different noise originations depending on magnetic anisotropies. With a small sensing area of 20×20 μm2, the best magnetic field detectability reaches 76 nT/Hz at 1 Hz and 2 nT/Hz at 10 kHz. AHE sensors with compensated magnetic anisotropies are, thus, suitable for ultrasensitive magnetic field sensing applications.
The interfacial Dzyaloshinskii-Moriya interaction (DMI) holds promises for design and control of chiral spin textures in low-dimensional magnets with efficient current-driven dynamics. Recently, an interlayer DMI has been found to exist across magnetic multilayers with a heavy-metal spacer between magnetic layers. This opens the possibility of chirality in these three-dimensional magnetic structures. Here we show the existence of the interlayer DMI in a synthetic antiferromagnetic multilayer with both inversion and in-plane asymmetry. We analyse the interlayer DMI’s effects on the magnetization and the current-induced spin-orbit torque (SOT) switching of magnetization through a combination of experimental and numerical studies. The chiral nature of the interlayer DMI leads to an asymmetric SOT switching of magnetization under an in-plane magnetic field. Our work paves the way for further explorations on controlling chiral magnetizations across magnetic multilayers through SOTs, which can provide a new path in the design of SOT devices.
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