Centrosymmetric GdRu2Si2 exhibits a variety of multi-Q magnetic states as a function of temperature and applied magnetic field, including a square skyrmion-lattice phase. The material's behavior is strongly dependent on the direction of the applied field, with different phase diagrams resulting for fields applied parallel or perpendicular to the crystallographic c axis. Here, we present the results of muon-spin relaxation (μ+SR) measurements on single crystals of GdRu2Si2. Our analysis is based on the computation of muon stopping sites and consideration of zero-point motion effects, allowing direct comparison with the underlying spin textures in the material. The muon site is confirmed experimentally, using angle-dependent measurements of the muon Knight shift. Using transverse-field μ+SR with fields applied along either the [001] or [100] crystallographic directions, we distinguish between the magnetic phases in this system via their distinct muon response, providing additional evidence for the skyrmion and meron-lattice phases, while also suggesting the existence of RKKY-driven muon hyperfine coupling. Zero-field μ+SR provides clear evidence for a transition between two distinct magnetically-ordered phases at 39 K.
@article{arxiv.2403.09431,
title = {Field-orientation-dependent magnetic phases in GdRu$_2$Si$_2$ probed with muon-spin spectroscopy},
author = {B. M. Huddart and A. Hernández-Melián and G. D. A. Wood and D. A. Mayoh and M. Gomilšek and Z. Guguchia and C. Wang and T. J. Hicken and S. J. Blundell and G. Balakrishnan and T. Lancaster},
journal= {arXiv preprint arXiv:2403.09431},
year = {2025}
}