Spin Wave Transmission by Spin Impurities in a Quasi-1D Heisenberg Ferromagnetic Tubular Structure

Abstract

This paper introduces a theoretical study to investigate, at a low temperature, the spin wave propagation and total magnon transmission via atomic substitution sites in a quasi-1D Heisenberg ferromagnetic tubular structure. The model system consists of four ordered ferromagnetic atomic chains, arranged in the space of a parallel manner two to two and containing a finite number of substitution sites, considered as spin impurities. The model is supported on a non-magnetic substrate and considered otherwise free from magnetic interactions with its environment. To describe the dynamics of the tubular structure, we used the theoretical matching procedure. The total transmission and reflection cross sections at the boundary containing the substitution sites are calculated and analyzed as a function of the incident frequency per propagating mode of the perfect quasi-1D tubular structure. The impurity observables are numerically calculated for different cases of softening and hardening to investigate how the local dynamics can respond to changes in the microscopic environment on the perturbed domain. Our results show the interferences between incident spin modes and the localized spin states of the substitution sites. The observe effects are induced by the modification of boundary magnetic exchange values and spin intensity of the impurity sites of the system. The results yield, also, an understanding for the relationship between the coherent magnon transmission and the position of the substitution spin sites in the studied structure.