Abstract
Antiferromagnets offer spintronic device characteristics unparalleled in ferromagnets owing to their lack of stray fields, THz spin dynamics, and rich materials landscape. Microscopic imaging of antiferromagnetic domains is one of the key prerequisites for understanding physical principles of the device operation. However, adapting common magnetometry techniques to the dipolar-field-free antiferromagnets has been a major challenge. Here we demonstrate in a collinear antiferromagnet a thermoelectric detection method by combining the magneto-Seebeck effect with local heat gradients generated by scanning far-field or near-field techniques. In a 20-nm epilayer of uniaxial CuMnAs we observe reversible 180∘ switching of the Néel vector via domain wall displacement, controlled by the polarity of the current pulses. We also image polarity-dependent 90∘ switching of the Néel vector in a thicker biaxial film, and domain shattering induced at higher pulse amplitudes. The antiferromagnetic domain maps obtained by our laboratory technique are compared to measurements by the established synchrotron-based technique of x-ray photoemission electron microscopy using x-ray magnetic linear dichroism.Received 5 June 2020Accepted 12 August 2020DOI:https://doi.org/10.1103/PhysRevMaterials.4.094413©2020 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAntiferromagnetismMagnetic domainsSeebeck effectSpintronicsPhysical SystemsAntiferromagnetsTechniquesAtomic force microscopyNear-field optical spectroscopyScanning techniquesCondensed Matter, Materials & Applied Physics
Highlights
Antiferromagnets offer spintronic device characteristics unparalleled in ferromagnets owing to their lack of stray fields, THz spin dynamics, and rich materials landscape
Writing and reading by electrical and optical means, high speed operation combined with neuromorphic memory characteristics, and novel topological phenomena are among the topics that have driven the research in the emerging field of antiferromagnetic spintronics[1,2,3,4,5,6]
In CuMnAs, the XMLD-PEEM images of the onset of current-induced Neel spin-orbit torque (NSOT) reorientation of the Neel vector were directly linked to the onset of the corresponding electrical readout signals due to AMR13,14. 90◦ Neel vector switching was observed by XMLD-PEEM for orthogonal writing currents[11,13] or, via domain wall motion, when reversing the polarity of the writing current[14]
Summary
Antiferromagnets offer spintronic device characteristics unparalleled in ferromagnets owing to their lack of stray fields, THz spin dynamics, and rich materials landscape. From the early days of the antiferromagnetic spintronics research, a special attention is paid to complementing these electrical measurements by direct microscopic imaging of the typically multidomain states of the studied antiferromagnets[11,13,14,15,16,17,18,19,20,21] The aim of these microscopies is to elucidate physical mechanisms of the switching which, e.g., in CuMnAs have been associated with the Neel vector reorientation induced by the NSOT, and with electrical or optical pulse-induced quenching into nano-fragmented domain states of the antiferromagnet[20,21]. To the best of our knowledge, the scanning optical microscopy combined with MSE has not been applied to antiferromagnets prior to our work, we provide comparisons to images obtained by the established synchrotron XMLD-PEEM technique
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