Probing short-range magnetic order in a geometrically frustrated magnet by means of the spin Seebeck effect

The spin Seebeck effect (SSE) can be used for generating pure spin currents in insulating magnetic materials using thermal gradients. Here, the authors exploit the sensitivity of SSE to local magnetic correlations to probe magnetic short-range order (SRO) in a geometrically frustrated paramagnet Gd${}₃$Ga${}₅$O${}₁₂$ (GGG). The authors find that the magnetic SRO in GGG exists at temperatures far above where the corresponding antiferromagnetic long-range order can be detected using neutron scattering. Many fundamentally interesting states such as quantum spin liquids and spin ice arise in geometrically frustrated magnets. However, characterizing magnetic order within these materials in the absence of long-range order has been technically challenging, with insights derived mostly from neutron scattering measurements. This work suggests that the SSE may be an effective probe of magnetic SRO in geometrically frustrated systems, complementary to neutron and x-ray scattering.