Abstract
We report the observation of magnon spin currents generated by the spin Seebeck effect (SSE) in a bulk single crystal of the easy-plane antiferromagnet NiO. A magnetic field induces a nondegeneracy and thereby an imbalance in the population of magnon modes with opposite spins. A temperature gradient then gives rise to a nonzero magnon spin current. This SSE is measured in both a local and a nonlocal geometry at 5 K in bulk NiO. The magnetic field dependence of the obtained signal is modeled by magnetic field splitting of the low-energy magnon modes, affecting the spin Seebeck coefficient. The relevant magnon modes at this temperature are linked to cubic anisotropy and magnetic dipole-dipole interactions. The nonlocal signal deviates from the expected quadratic Joule heating by saturating at a current from around 75 mu A in the injector. The magnon chemical potential does not decay exponentially with distance and inhomogeneities may be the result of local magnon accumulations.
Original language | English |
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Article number | 214415 |
Number of pages | 6 |
Journal | Physical Review B |
Volume | 102 |
Issue number | 21 |
DOIs | |
Publication status | Published - 14-Dec-2020 |