Thermal generation of spin current in a helimagnetic multiferroic hexaferrite

TL;DR

This study demonstrates that helimagnetic spin waves can generate spin currents via the spin Seebeck effect, and these currents are robust against domain wall effects, with potential implications for spintronic devices.

Contribution

It provides experimental evidence that helimagnetic spin waves effectively carry spin current and are unaffected by spin-helicity domain walls, unlike ferromagnetic domain walls.

Findings

Spin Seebeck effect observed in helimagnetic multiferroic Ba0.5Sr1.5Zn2Fe12O22.

Spin current magnitude correlates with bulk magnetization across magnetic phases.

Spin-helicity domain distribution does not influence spin current magnitude.

Abstract

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.