Thermally driven long-range magnon spin currents in yttrium iron garnet due to intrinsic spin Seebeck effect

Although recent experiments and theories have shown a variety of exotic transport properties of nonequilibrium quasiparticles (QPs) in superconductor (SC)-based devices with either Zeeman or exchange spin-splitting, how a QP interplays with magnon spin currents remains elusive. Here, using nonlocal magnon spin-transport devices where a singlet SC (Nb) on top of a ferrimagnetic insulator (Y3Fe5O12) serves as a magnon spin detector, we demonstrate that the conversion efficiency of magnon spin to QP charge via inverse spin-Hall effect (iSHE) in such an exchange-spin-split SC can be greatly enhanced by up to 3 orders of magnitude compared with that in the normal state, particularly when its interface superconducting gap matches the magnon spin accumulation. Through systematic measurements by varying the current density and SC thickness, we identify that superconducting coherence peaks and exchange spin-splitting of the QP density-of-states, yielding a larger spin excitation while retaining a modest QP charge-imbalance relaxation, are responsible for the giant QP iSHE. The latter exchange-field-modified QP relaxation is experimentally proved by spatially resolved measurements with varying the separation of electrical contacts on the spin-split Nb.

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“…Furthermore, the energy-dependent magnon diffusion and relaxation of the YIG channel may play a role in the transport process. 27 , 28 …”

Section: Resultsmentioning

confidence: 99%

Giant Transition-State Quasiparticle Spin-Hall Effect in an Exchange-Spin-Split Superconductor Detected by Nonlocal Magnon Spin Transport

Jeon

Zhou

et al. 2020

ACS Nano

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“…NL stands for the nonlocal SSE. 3,15,[36][37][38][39][40] The conductance of the NFO thin films was checked by measuring resistances between random pairs of electrically detached contacts, which yielded values over GΩ, confirming the insulating nature of the NFO films.…”

Section: And V 2fmentioning

confidence: 92%

Enhanced magnon spin transport in NiFe2O4 thin films on a lattice-matched substrate

Shan

Singh

Lei

et al. 2018

Applied Physics Letters

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We investigate magnon spin transport in epitaxial nickel ferrite (NiFe 2 O 4 , NFO) films grown on magnesium gallate spinel (MgGa 2 O 4 , MGO) substrates, which have a lattice mismatch with NFO as small as 0.78%, resulting in the reduction of antiphase boundary defects and thus in improved magnetic properties in the NFO films. In the nonlocal transport experiments, enhanced signals are observed for both electrically and thermally excited magnons, and the magnon relaxation length (λ m ) of NFO is found to be around 2.5 µm at room temperature. Moreover, at both room and low temperatures, we present distinct features from the nonlocal spin Seebeck signals which arise from magnonpolaron formation. Our results demonstrate excellent magnon transport properties (magnon spin conductivity, λ m and spin mixing conductance at the interface between Pt) of NFO films grown on a lattice-matched substrate that are comparable with those of yttrium iron garnet.

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“…More recently, Uchida and co-authors showed that a pure spin flow can be generated in a magnetic insulator not only via electrical injection, but by heat gradients as well via the spin Seebeck effect (SSE) [12], suggesting the possibility of converting waste heat into spin signals and, thus, opening up intriguing prospects for "greener" information technology [13]. Experimental observations of electrically-and thermallygenerated spin transport have confirmed the potential of magnetic insulating systems as long-range information carriers [14][15][16][17].…”

Section: Introductionmentioning

confidence: 96%

Long-distance transport of magnon spin information in a magnetic insulator at room temperature

et al. 2015

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The transport of spin information has been studied in various materials, such as metals 1 , semiconductors 2 and graphene 3 . In these materials, spin is transported by diffusion of conduction electrons 4 . Here we study the diffusion and relaxation of spin in a magnetic insulator, where the large bandgap prohibits the motion of electrons. Spin can still be transported, however, through the diffusion of non-equilibrium magnons, the quanta of spin wave excitations in magnetically ordered materials. Here we show experimentally that these magnons can be excited and detected fully electrically 5,6 in linear response, and can transport spin angular momentum through the magnetic insulator yttrium iron garnet (YIG) over distances as large as 40 μm. We identify two transport regimes: the diffusion limited regime for distances shorter than the magnon relaxation length, and the relaxation limited regime for larger distances. With a model similar to the diffusion-relaxation model for electron spin transport in (semi)conducting materials, we extract the magnon relaxation length = . ± . μm in a 200 nm thin YIG film at room temperature.

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Thermally driven long-range magnon spin currents in yttrium iron garnet due to intrinsic spin Seebeck effect

Cited by 35 publications

References 21 publications

Giant Transition-State Quasiparticle Spin-Hall Effect in an Exchange-Spin-Split Superconductor Detected by Nonlocal Magnon Spin Transport

Giant Transition-State Quasiparticle Spin-Hall Effect in an Exchange-Spin-Split Superconductor Detected by Nonlocal Magnon Spin Transport

Enhanced magnon spin transport in NiFe2O4 thin films on a lattice-matched substrate

Long-distance transport of magnon spin information in a magnetic insulator at room temperature

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