Non-Local Spin Transport Driven by Spin Seebeck Effect in a Heisenberg Antiferromagnet

In contrast to the tremendous success of spintronics in the non-volatile data storage, transport and processing of data via the spin degree of freedom have not excelled proportionally. Such an imbalance stems primarily from the short (< 1µm) diffusion length of spin carried by conduction electrons in (magnetic) metals, which are integral building blocks of contemporary spintronic devices such as spin valves. This shortcoming has turned attentions towards the use of magnetic insulators in which, instead of conduction electrons, information can be carried over a longer distance by the collective excitations of atomic spins, that is the spin wave.

Here we demonstrate the long-distance transport of spin via the collective excitations of atomic spins in a Heisenberg antiferromagnetic insulator (AFI). We show that a temperature gradient across the AFI drives a spin Seebeck current that can travel and be measured at a long distance away from the heat source via the conversion of the spin current into a charge current through the inverse spin Hall effect in a heavy metal in contact with the AFI. Our temperature-dependent measurements reveal two phenomenologically different spin transport regimes at low and high temperatures that we will explain using the spin Seebeck effect.