Nuclear spin Seebeck effect in antiferromagnets

The spin Seebeck effect (SSE) involves transfer of spin angular momentum between a magnet and a metal from internal thermal fluctuations. SSE is usually dominated by electronic, rather than nuclear, spins, since interfacial exchange is much stronger than interfacial hyperfine coupling. At low temperatures, however, electronic magnon thermal occupation numbers are exponentially suppressed, while nuclear spins remain active. The nuclear spins are paramagnetic, weakly polarized in the large hyperfine field of the Neel order. One source for nuclear SSE is interfacial nuclear, metal spin flip-flops, known as Korringa relaxation. Nuclear SSE is then determined by competing rates: thermalization with phonons via hyperfine coupling to electrons in the magnet, and Korringa relaxation into the metal.