November 07, 2022
Minneapolis, United States
Néel spin orbit torque induced remnant switching of the Néel vector in antiferromagnetic Mn2Au
Antiferromagnets (AFMs) are strong candidates for future spintronic applications largely because of their fast dynamics and lack of stray fields. For the required switching of the Néel vector (staggered magnetization), the predicted current-induced bulk Néel spin-orbit torque (NSOT) (1) is most promising. Only two compounds with the required symmetry are known: for both CuMnAs (2,3) and Mn2Au (4,5) experimental evidence for current-induced NSOT was shown based on a small modification of the AFM domain pattern. However, the significance of NSOT for current-induced manipulation of Neel vector orientation stays controversial because competing heating-related mechanisms result in similar effects (6-8).
Here, we investigate the effect of current pulsing with different lengths along the different crystallographic directions on the AFM domain pattern of epitaxial Mn2Au (001) thin films. In-situ imaging of AFM domains before and after the current pulses was performed using x-ray magnetic linear dichroism photoemission electron microscopy (XMLD-PEEM). Reversible and repeated 90° Neel vector rotation of essentially the complete active area of the pattern cross structures was observed (Fig. 1).
Switching was only observed for current parallel to the easy crystallographic axis resulting in a Néel vector rotation perpendicular to the pulse direction, which is consistent with the NSOT. The required current density for switching is essentially independent of the pulse length (10 µs to 1 ms) indicating that thermal activation or other thermal effects are not significant. For current pulses applied parallel to a <100> hard axis, inversion of the current pulse polarity led to a partially reversible motion of domain walls, which is consistent with the NSOT acting on them. Our results confirm the fundamental role of NSOT for current-induced Néel vector switching in Mn2Au, providing an effective mechanism for spintronics applications.
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