Field-orientation-dependent magnetic phases in GdRu2鈦i2 probed with muon-spin spectroscopy
Abstract:
Centrosymmetric聽GdRu2鈦i2聽exhibits a variety of multi-饾憚聽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聽饾憪聽axis. Here, we present the results of muon-spin relaxation (饾渿+鈦R) measurements on single crystals of聽GdRu2鈦i2. Our analysis is based on the computation of muon stopping sites and consideration of quantum zero-point motion effects of muons, 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聽饾渿+鈦R聽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聽饾渿+鈦R聽provides clear evidence for a transition between two distinct magnetically ordered phases at 39 K.Spin dynamics in the Dirac $U(1)$ spin liquid YbZn$_2$GaO$_5$
Anisotropic skyrmion and multi-q spin dynamics in centrosymmetric Gd2PdSi3
Abstract:
Skyrmions are particlelike vortices of magnetization with nontrivial topology, which are usually stabilized by Dzyaloshinskii-Moriya interactions (DMI) in noncentrosymmetric bulk materials. Exceptions are centrosymmetric Gd- and Eu-based skyrmion-lattice (SL) hosts with zero DMI, where both the SL stabilization mechanisms and magnetic ground states remain controversial. We address these here by investigating both the static and dynamical spin properties of the centrosymmetric SL host聽Gd2鈦诲厂颈3聽using muon spectroscopy. We find that spin fluctuations in the noncoplanar SL phase are highly anisotropic, implying that spin anisotropy plays a prominent role in stabilizing this phase. We also observe strongly anisotropic spin dynamics in the ground-state (IC-1) incommensurate magnetic phase of the material, indicating that it hosts a meronlike multi-q structure. In contrast, the higher-field, coplanar IC-2 phase is found to be single q聽with nearly isotropic spin dynamics.