We report the experimental observation of longitudinal spin Seebeck effect in
a multiferroic helimagnet Ba0.5Sr1.5Zn2Fe12O22. Temperature gradient applied
normal to Ba0.5Sr1.5Zn2Fe12O22/Pt interface generates inverse spin Hall voltage
of spin current origin in Pt, whose magnitude was found to be proportional to
bulk magnetization of Ba0.5Sr1.5Zn2Fe12O22 even through the successive magnetic
transitions among various helimagnetic and ferrimagnetic phases. This finding
demonstrates that the helimagnetic spin wave can be an effective carrier of
spin current. By controlling the population ratio of spin-helicity domains
characterized by clockwise/counter-clockwise manner of spin rotation with use
of poling electric field in the ferroelectric helimagnetic phase, we found that
spin-helicity domain distribution does not affect the magnitude of spin current
injected into Pt. The results suggest that the spin-wave spin current is rather
robust against the spin-helicity domain wall, unlike the case with the
conventional ferromagnetic domain wall.Comment: 12 pages, 4 figure
