Nonreciprocal spin wave propagation in chiral-lattice ferromagnets

TL;DR

This paper demonstrates nonreciprocal spin wave propagation in chiral-lattice ferromagnets, revealing how chirality and spin-orbit interactions enable diode-like control of spin currents, advancing spintronics technology.

Contribution

It provides the first experimental evidence of nonreciprocal spin wave spin current in chiral ferromagnets due to spin-orbit interaction and lattice chirality.

Findings

Nonreciprocal spin wave propagation observed

Chirality and spin-orbit interaction cause interference effects

Potential for designing spin current diodes

Abstract

Spin current, i.e. the flow of spin angular momentum or magnetic moment, has recently attracted much attention as the promising alternative for charge current with better energy efficiency. Genuine spin current is generally carried by the spin wave (propagating spin precession) in insulating ferromagnets, and should hold the chiral symmetry when it propagates along the spin direction. Here, we experimentally demonstrate that such a spin wave spin current (SWSC) shows nonreciprocal propagation characters in a chiral-lattice ferromagnet. This phenomenon originates from the interference of chirality between the SWSC and crystal-lattice, which is mediated by the relativistic spin-orbit interaction. The present finding enables the design of perfect spin current diode, and highlights the importance of the chiral aspect in SWSC.