Spin transport in insulators without exchange stiffness

Abstract

The discovery of new materials that efficiently transmit spin currents has been important for spintronics and material science. The electric insulator Gd3Ga5O12 (GGG), a standard substrate for growing magnetic films, can be a spin current generator, but has never been considered as a superior conduit for spin currents. Here we report spin current propagation in paramagnetic GGG over several microns. Surprisingly, spin transport persists up to temperatures of 100 K Tg = 180 mK, the magnetic glass-like transition temperature of GGG. At 5 K and 3.5 T, we find a spin diffusion length λGGG = 1.8 ± 0.2 μm and a spin conductivity σGGG = (7.3 ± 0.3) × 104 Sm−1 that is larger than that of the record quality magnet Y3Fe5O12 (YIG). We conclude that exchange stiffness is not required for efficient spin transport, which challenges conventional models and provides new material-design strategies for spintronic devices.

Magnetic order of Dy3+ and Fe3+ moments in antiferromagnetic DyHoogeboom1, Kuschel2, Bauer3 et al. 2021Phys. Rev. B17071View full textAdd to dashboardCite

“…with σ m as the magnon spin conductivity and S S the spin Seebeck coefficient. Thermal magnons can typically diffuse over several μm [36][37][38], which implies that the SSE mainly probes bulk rather than interface magnetic properties. The magnons in simple AFMs typically come in degenerate pairs with opposite polarization that split under an applied magnetic field [11,39].…”

“…The associated imbalance of the magnon populations cause a nonzero spin Seebeck effect [13]. Paramagnets display a field-induced SSE effect [38] for the same reason, so aligned Dy 3+ moments can contribute to an SSE in DFO.…”

“…A net magnetization of rare-earth moments affects the SSE signals in gadolinium iron [47] and gadolinium gallium [38] garnets. We assume that the SSE is dominated by a spin current from the bulk that is proportional to the total magnetization m Dy b of the four Dy sublattices that we calculated for the Hamiltonian Eq.…”

Магнон-Фононное Взаимодействие В Переходном Слое Эпитаксиальной Пленки ЖИГ

“…Дальнейшее развитие магнонной спинтроники стимулирует поиск новых механизмов транспорта спинового момента [1]. В частности исследуются возможности переноса спина когерентными фононами в композитных структурах, состоящих из ферромагнитных и акустических слоев [2,3]. Такие структуры получили название магнитоакустические метаматериалы [4].…”

Focused ion beam modification of non-local magnon-based transport in yttrium iron garnet/platinum heterostructures

“…There have been several reports of a large SMR or MMR in heterostructures of a HM and a disordered or paramagnetic magnetic insulator. [22][23][24][25][26] However, other experiments showed that in the absence magnetic ordering no MMR can be observed. 27,28 From the theory side, microscopic models to describe the temperature dependence of the SMR have been put forward and good agreement with experiments was found for different material systems.…”