Optically-triggered strain-driven Néel vector manipulation in a metallic antiferromagnet

Abstract

The absence of stray fields, their insensitivity to external magnetic fields, and ultrafast dynamics make antiferromagnets promising candidates for active elements in spintronic devices. Here, we demonstrate manipulation of the Néel vector in the metallic collinear antiferromagnet Mn 2 Au by combining strain and femtosecond laser excitation. Applying tensile strain along either of the two in-plane easy axes and locally exciting the sample by a train of femtosecond pulses, we align the Néel vector along the direction controlled by the applied strain. The dependence on the laser fluence and strain suggests the alignment is a result of optically-triggered depinning of 90 o domain walls and their sliding in the direction of the free energy gradient, governed by the magneto-elastic coupling. The resulting, switchable, state is stable at room temperature and insensitive to magnetic fields. Such an approach may provide ways to realize robust high-density memory device with switching timescales in the picosecond range.Antiferromagnets (AFM) have recently attracted major scientific interest due to their prospective applications in the field of spintronics. [1][2][3][4] For information storage, they offer several advantages over ferromagnets, such as a potential for ultrafast switching, the lack of stray fields and, thus, the robustness against external fields. All these properties could enable high information density, with the direction of the staggered magnetization (Néel vector, L) as the information carrier. The lack of sensitivity to external magnetic fields, however, poses challenges in terms of writing [5][6][7] and read-out [7][8][9][10][11] schemes. Exploring the ways to rapidly and reliably manipulate the Néel vector direction is at the heart of the current AFM spintronics research. [1][2][3][4] Especially the metallic collinear antiferromagnets CuMnAs and Mn 2 Au, which enable current-induced bulk (Néel) spin-orbit torques, 12 have been in the focus of recent research. Several approaches for switching the direction of the Néel vector have been suggested, which include aligning the Néel vector by high magnetic fields, 13, 14 application of strain, 15,16 and, most prominently, using current-driven Néel spin-orbit torques. [5][6][7] In terms of the read-out, in addition to X-ray magnetic linear dichroism, 13,16,17 electrical read-out via the anisotropic magnetoresistance (AMR) 5, 7 and optical magnetic linear dichroism (OMLD) 10,18 have been realized. In spite the achieved progress, an ultrafast approach for locally changing the Néel vector orientation is needed to fully exploit the potential of AFMs in spintronics.

Optically Triggered Néel Vector Manipulation of a Metallic Antiferromagnet Mn2Au under Strain

“…The resulting XMLD-PEEM images were obtained by pixelwise division of XMLD contrast maps recorded at 638.6 and 637.6 eV, where each XMLD was determined by the normalized difference of images acquired with the two orthogonal X-ray polarizations. The field of view used is 20 μm …”