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

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 Neél 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 Neél 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°domain walls and their motion 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 highdensity memory device with switching time scales in the picosecond range.

Current-driven writing process in antiferromagnetic Mn2Au for memory applications

“…1 and 2) . However, also thermomagnetoelastic coupling effects driven by anisotropic strain due to current heating can generate this type of Néel vector reorientation 22 , as the Néel vector prefers alignment along an elongated 〈110〉 direction 19 . In principle, thermomagnetoelastic coupling and NSOT can cooperate for stripe and cross geometries aligned along 〈110〉 directions.…”

“…However, it later became clear that alternative mechanisms such as current pulse induced heat effects 14,15 , electromigration 16 , and rapid quenching induced structural and magnetic modifications 17 can result in resistance modifications similar to the ones reported as well. Additionally, external strain supported Néel vector manipulation in Mn 2 Au was demonstrated 18,19 . Thus, microscopic investigations showing the intended current driven alignment of the staggered magnetization directly are essential.…”

The Impact of Local Strain Fields in Noncollinear Antiferromagnetic Films

“…Recently there has been great interest in antiferromagnetic materials for their use in energy efficient computing [1][2][3][4] and neuromorphic hardware [5,6] with the potential for terahertz operating frequencies, lower thermal losses, and enhanced on-chip packing density. [7][8][9][10] In particular, noncollinear antiferromagnets (AFMs) such as Mn 3 A (A = Sn, Ge, Pt) and Mn 3 AN (A = Ni, Ga, Sn) have been shown to possess intrinsic anomalous Hall effect (AHE), [11][12][13][14][15][16][17] magneto-optical Kerr effect (MOKE), [18][19][20] anomalous Nernst effect (ANE), [21][22][23] and the tunneling magnetoresistance effect [24] which allows for easy readout of the antiferromagnetic state, an obstacle for many collinear antiferromagnetic families, [25][26][27] although encouraging progress with altermagnets may help overcome this bottleneck. [28][29][30][31] Although it is theoretically understood that the AHE may be observed in fully compensated noncollinear AFM with M = 0, [32][33][34][35] experimentally the observation of the anomalous Hall effect in noncollinear AFM systems is accompanied with a small net moment.…”

Photocurrents, inverse Faraday effect and photospin Hall effect in Mn$_2$Au

“…Optically-driven dynamical properties of Mn 2 Au have become a target of recent attention as well. For example, recently, an optical manipulation of magnetic order in Mn 2 Au has been achieved by a combination of laser pulses and strain 20,21 . However, in order to move forward in pursuing optical implementations based on Mn 2 Au, it is important to understand in detail the optical response of this material, in particular the behavior of photocurrents and inverse Faraday effect, in relation to its electronic and magnetic structure.…”