Omnidirectional Control of Large Electrical Output in a Topological Antiferromagnet

Abstract

Control of magnetization direction is essential for the wide application of ferromagnets; it defines the signal size of memory and sensor. However, the magnetization itself causes a dilemma. While its size matters to obtain strong responses upon its reversal, the large magnetization concomitantly suppresses the range of its directional control because of the demagnetizing field. On the other hand, realization of the desired magnetic anisotropy requires careful engineering of crystalline and interfacial effects to overcome the demagnetization barrier. Thus, it would be ideal if one could find alternative magnets that carry no magnetization but strong responses. The discovery of a topological metallic state in the antiferromagnet Mn3Sn is significant; they host a large Berry curvature in momentum space, enabling the observation of disproportionately large transverse responses such as anomalous Hall and Nernst effects, the key functionalities for replacing ferromagnets in the magnetic devices. Here, the experimental realization of omnidirectional control of the large responses in an antiferromagnet is reported. In particular, it is demonstrated that the absence of shape anisotropy enables the omnidirectional control, and lifts the shape constraint in designing the magnetic devices. This work lays the technological foundation for developing simple‐structured high‐performance devices including multi‐level memory and heat flux sensor.

Seebeck-driven transverse thermoelectric generation

“…One of the well-known transverse thermoelectric phenomena is the anomalous Nernst effect (ANE) observed in magnetic materials . In addition to exploit it for thermoelectric generation, there has been effort to explore other functionalities, such as heat flux sensing [22,29].…”

Anomalous Hall antiferromagnets

“…They have also demonstrated electrical and optical writing pulse-lengths from millisecond to femtosecond, analog time-dependent logic-in-memory functionalities reminiscent of neuromorphic computing elements, and in-formation coding into metastable atomic-scale magnetic textures. 59,[61][62][63][65][66][67][68][69][70][71]174,175 Ferromagnetic digital memories, on the other hand, owe their commercial success primarily to the giant magnetoresistive readout signals and efficient spin transfer torque writing, relying on spinconserving electron transport. [92][93][94][95][96] The discovery of the Hall effect in the compensated collinear magnets has led directly to a theory proposal that the essential spintronic reading and writing principles based on conserved spin-currents should be readily available in these systems.…”

Topological Magnets: Functions Based on Berry Phase and Multipoles

“…As FM memory devices reach limits of miniaturization, the use of antiferromagnets would allow for even higher storage density. In addition, without stray fields, antiferromagnets are free from shape anisotropy (87), which is in sharp contrast with ferromagnets. Furthermore, antiferromagnets have much faster spin dynamics than ferromagnets, opening new avenues for ultrafast data processing.…”