Spin Seebeck effect in the polar antiferromagnet α−Cu2V2O7

We have studied the longitudinal spin Seebeck effect in a polar antiferromagnet α−Cu2V2O7 in contact with a Pt film. Below the antiferromagnetic transition temperature of α−Cu2V2O7, spin Seebeck voltages whose magnetic-field dependence is similar to that reported in antiferromagnetic MnF2|Pt bilayers are observed. Though a small weak-ferromagnetic moment appears owing to the Dzyaloshinskii-Moriya interaction in α−Cu2V2O7, the magnetic-field dependence of spin Seebeck voltages is found to be irrelevant to the weak-ferromagnetic moments. The dependences of the spin Seebeck voltages on magnetic fields and temperature are analyzed by a magnon spin-current theory. The numerical calculation of spin Seebeck voltages using magnetic parameters of α−Cu2V2O7 determined by previous neutron-scattering studies reveals that the magnetic-field and temperature dependences of the spin Seebeck voltages for α−Cu2V2O7|Pt are governed by the changes in magnon lifetimes with magnetic fields and temperature.