Phys. Rev. Lett. 115, 266601 (2015)

Phys. Rev. Lett. 116, 097204 (2016)

A key phenomenon in the field of spin caloritronics is the spin Seebeck effect — the generation of a spin current triggered by a thermal gradient — that typically develops in bilayers made from ferromagnets. The phenomenon has been observed with antiferromagnetically correlated paramagnetic materials. Theoretical predictions suggest that a similar effect could also be induced with long-range-ordered antiferromagnets below the critical Néel temperature, and this could lead to the development of faster and higher-performance spintronic devices. Two independent research groups have now confirmed these proposals using heterostructures based on typical antiferromagnetic insulating materials.

Shinichiro Seki and colleagues at the RIKEN Center for Emergent Matter Science and other institutes in Japan studied Cr2O3/Pt junctions whereas Stephen Wu and colleagues at the Argonne National Laboratory and West Virginia University focused on MnF2/Pt junctions. In both cases, the researchers simultaneously applied in-plane magnetic fields and transverse temperature gradients, detecting non-zero spin Seebeck voltages along the Pt. From marked anomalies at high magnetic fields, unambiguous evidence was provided for the development of a spin-flopped phase for the uniaxial antiferromagnets, in excellent agreement with independent characterizations of the bulk materials. These results show the influence of the antiferromagnetic spin waves on the spin currents developing in Pt.