A generalized model of magnon kinetics for two-dimensional spin transport

Long-distance spin transport is highly desirable for spintronic applications. In magnetic insulators, spin transport is dominated by the kinetics of magnon excitations. Here, we present a generalized model of magnon kinetics applicable across a wide range of length scales [1]. Based on a Boltzmann theory considering both spin-conserving magnon collisions and magnon-decay processes hence spin relaxation, our result reproduces the phenomenological spin diffusion equation in the long-distance diffusive limit and the Lindhard formalism in the short-distance ballistic limit, while providing a prediction for the intermediate regime, which can be explored with magnetic noise measurement using, e.g. nitrogen-vacancy centers [2]. The transport properties extracted from our theory also provides some insights to the recent experimental report of enhanced spin conductivity in magnetic thin films approaching two dimensions [3].

1. Fang, H., Zhang, S. & Tserkovnyak, Y. Generalized model of magnon kinetics and subgap magnetic noise. Phys. Rev. B 105, 184406 (2022).

2. H Wang, S Zhang, NJ McLaughlin, B Flebus, M Huang, Y Xiao, C Liu, M. Wu, E. E. Fullerton, Y. Tserkovnyak, C. R. Du, Sci. Adv. 8 (1), eabg8562 (2022).

3. Wei, XY., Santos, O.A., Lusero, C.H.S. et al. Giant magnon spin conductivity in ultrathin yttrium iron garnet films. Nat. Mater. (2022).