Interaction of gapless spin waves and a domain wall in an easy-cone ferromagnet

TL;DR

This paper theoretically investigates how gapless spin waves interact with a domain wall in an easy-cone ferromagnet, revealing finite reflection, and demonstrates thermally-driven domain-wall motion at low temperatures due to these unique spin waves.

Contribution

It introduces the first analysis of gapless spin wave scattering on domain walls in easy-cone magnets and explores their role in low-temperature magnonic dynamics.

Findings

Gapless spin waves exhibit finite reflection at domain walls.

Thermal bias can drive domain-wall motion via magnonic torque.

Low-temperature domain-wall motion is possible due to gapless spin waves.

Abstract

We theoretically study the interaction of spin waves and a domain wall in a quasi-one-dimensional easy-cone ferromagnet. The gapless spin waves on top of a domain wall are found to exhibit finite reflection in contrast to the well-known perfect transmission of gapful spin waves in easy-axis magnets. Based on the obtained scattering properties, we study the thermal-magnon-driven dynamics of a domain wall subjected to a thermal bias within the Landau-B\"uttiker formalism, where transmitted magnons are shown to exert the magnonic torque on the domain wall and thereby drive it with the velocity linear to the applied thermal bias. The peculiar gapless nature of spin waves in easy-cone magnets enables the thermally-driven domain-wall motion even at low temperatures, differing from the easy-axis case where the domain-wall velocity is exponentially suppressed at low temperatures. Our work suggests that easy-cone magnets can serve as a useful platform to study the interaction of gapless spin waves and nonlinear excitations and thereby realize low-temperature magnon-related phenomena.