How to Switch an Antiferromagnet
The magnetizations of the two sublattices that make up an antiferromagnet point in opposite directions, cancelling each other out. But if one of the sublattices breaks inversion symmetry, then flipping both yields a configuration that has different transport properties. With that difference comes the possibility of exploiting antiferromagnets to store and process information. Now Martin Jourdan of Johannes Gutenberg University Mainz in Germany and his collaborators have found that two different magnetization-flipping mechanisms operate on different timescales [1]. Their results suggest that the flipping mechanism has been misidentified in previous studies.
Researchers usually aim to flip an antiferromagnet between states by applying pulses of spin-polarized current. These currents cause the sublattice magnetizations to twist into new configurations via a phenomenon known as spin–orbit torque (SOT). However, it was recently found that, if the pulses are long enough, the mechanical strain caused by resistive heating can snap the sublattices into new configurations with or without SOT.
Jourdan and his collaborators investigated these mechanisms in thin films of the antiferromagnet Mn2Au. This material is triply advantageous for such studies: It’s a conductor, its manganese sublattices break inversion symmetry, and its gold sublattices host electrons whose strong spin–orbit coupling makes them especially sensitive to SOT.
The team distinguished between the two flipping mechanisms by measuring the magnetic domain patterns after applying current pulses with different orientations. SOT-induced flipping is sensitive to the current orientation; heating-induced flipping is not. The researchers found that pulses of 2.5 nanoseconds (ns) yielded the SOT pattern, whereas pulses of 100 ns and longer yielded the other, thermomagnetoelastic pattern. Jourdan says that previous experiments have all used current pulses longer than 1 microsecond, so they were probably in the latter regime.
–Charles Day
Charles Day is a Senior Editor for Physics Magazine.
References
- M. Jourdan et al., “Identifying switching of antiferromagnets by spin-orbit torques,” Phys. Rev. B 112, 104408 (2025).