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arXiv · 2106.09924

Exchange bias without directional anisotropy in Permalloy/CoO bilayers

Alexander Mitrofanov·Guanxiong Chen·Alexander Kozhanov·Sergei Urazhdin
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Abstract

We utilize transverse ac susceptibility measurements to characterize magnetic anisotropy in archetypal exchange-bias bilayers of ferromagnet Permalloy (Py) and antiferromagnet CoO. Unidirectional anisotropy is observed for thin Py, but becomes negligible at larger Py thicknesses, even though the directional asymmetry of the magnetic hysteresis loop remains significant. Additional magnetoelectronic measurements, magneto-optical imaging, as well as micromagnetic simulations show that these surprising behaviors are likely associated with asymmetry of spin flop distribution created in CoO during Py magnetization reversal, which facilitates the rotation of the latter back into its field-cooled direction. Our findings suggest new possibilities for efficient realization of multistable nanomagnetic systems for neuromorphic applications.

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Alexander Mitrofanov, Guanxiong Chen, Alexander Kozhanov, Sergei Urazhdin. 2021-06-18. Exchange bias without directional anisotropy in Permalloy/CoO bilayers. https://doi.org/10.1103/physrevb.104.144413

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