Abstract
Antiferromagnets are enriching spintronics research by many favorable properties that include insensitivity to magnetic fields, neuromorphic memory characteristics, and ultra-fast spin dynamics. Designing memory devices with electrical writing and reading is one of the central topics of antiferromagnetic spintronics. So far, such a combined functionality has been demonstrated via 90° reorientations of the Néel vector generated by the current-induced spin orbit torque and sensed by the linear-response anisotropic magnetoresistance. Here we show that in the same antiferromagnetic CuMnAs films as used in these earlier experiments we can also control 180° Néel vector reversals by switching the polarity of the writing current. Moreover, the two stable states with opposite Néel vector orientations in this collinear antiferromagnet can be electrically distinguished by measuring a second-order magnetoresistance effect. We discuss the general magnetic point group symmetries allowing for this electrical readout effect and its specific microscopic origin in CuMnAs.
Highlights
Antiferromagnets are enriching spintronics research by many favorable properties that include insensitivity to magnetic fields, neuromorphic memory characteristics, and ultra-fast spin dynamics
Electrical detection of the 180° spin reversal, which is the basis of the operation of ferromagnetic memories[1], has been among the outstanding challenges in the research of antiferromagnetic spintronics[2,3,4,5]
Anomalous Hall effect (AHE), which has been recently employed for spin reversal detection in non-collinear antiferromagnets, is limited to materials that crystalize in ferromagnetic symmetry groups[6,7,8,9,10,11]
Summary
Antiferromagnets are enriching spintronics research by many favorable properties that include insensitivity to magnetic fields, neuromorphic memory characteristics, and ultra-fast spin dynamics. Designing memory devices with electrical writing and reading is one of the central topics of antiferromagnetic spintronics Such a combined functionality has been demonstrated via 90° reorientations of the Néel vector generated by the current-induced spin orbit torque and sensed by the linear-response anisotropic magnetoresistance. The phenomenology of the non-linear transport effect we observe in CuMnAs is consistent with a microscopic scenario combining anisotropic magnetoresistance (AMR) with a transient tilt of the Néel vector due to a current-induced, staggered spinorbit field[6,12,13]. Later in the discussion part, we show that this microscopic mechanism is consistent with a general symmetrybased picture in which the spin reversal detection by a second-order magnetoresistance is allowed in antiferromagnets ordering in magnetic point groups with broken time and space inversion symmetry. We note that the analogous writing method was used in earlier studies of 90° Néel vector reorientation in CuMnAs and Mn2Au, controlled in this geometry by two orthogonal writing current lines and detected by the linear-response AMR12,13,15–18
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