Coexistence of long-range magnetic order and dynamical magnetism in the V-based Kagome metals: A combined thermodynamic and $μ$SR study

TL;DR

The paper investigates V-based Kagome metals RV$_6$Sn$_6$ (R = Tb, Dy, Ho, Er) to understand how 4f rare-earth anisotropy interacts with a nonmagnetic V Kagome layer. Using heat capacity and μSR, complemented by hyperfine analysis, it reports long-range magnetic order developing below 4 K in all compounds while revealing persistent low-energy spin fluctuations inside the ordered state. TbV$_6$Sn$_6$ shows coherent μSR oscillations indicative of a well-defined static field, whereas DyV$_6$Sn$_6$ lacks oscillations and exhibits strong field inhomogeneity, highlighting ion-specific dynamics. The results underscore a magnetism driven by 4f anisotropy in a Kagome lattice and establish RV$_6$Sn$_6$ as a clean platform to study anisotropy-driven spin dynamics, contrasting with Mn-based Kagome systems and pointing to rich physics arising from the decoupled rare-earth sublattice.

Abstract

V-based Kagome metals exhibit a unique lattice geometry that can give rise to exotic electronic and magnetic phenomena, making them an ideal platform to study the interplay of topology and magnetism. We present a combined thermodynamic and muon spin relaxation ($μ$SR) investigation of single-crystal RV$_{6}$Sn$_{6}$ (R = Tb, Dy, Ho, Er) compounds, focusing on their low-temperature magnetic behavior. Heat capacity and $μ$SR measurements reveal distinct magnetic phase transitions below 4 K, confirming the emergence of long-range magnetic order in all compounds studied. The $μ$SR results further indicate persistent spin fluctuations within the magnetically ordered state down to 50 mK, reflected in reduced ordered moments obtained from hyperfine analysis of the heat capacity measurements. These findings uncover the coexistence of static and dynamic magnetism in V-based Kagome metals and emphasizing the key role of 4$f$-electron anisotropy in shaping their magnetic ground states. Compared with the Mn-based RMn$_{6}$Sn$_{6}$ analogs, our results highlight the unique magnetism arising from the decoupled rare-earth sublattice and its interplay with the nonmagnetic V Kagome network.

Figures (4)

• Figure 1: Temperature dependence of the total specific heat C$_{p}$(T) of RV$_{6}$Sn$_{6}$ (R= Tb, Dy, Ho, Er and Lu) compounds measured at zero field down to 50 mK.
• Figure 2: (Symbol) Specific heat C$_{p}$ in TbV$_{6}$Sn$_{6}$, HoV$_{6}$Sn$_{6}$ and ErV$_{6}$Sn$_{6}$ systems. The curve below T$_{C/N}$ is fitted with the sum of T$^{3}$ and of a nuclear Schottky anomaly, the later being also computed with hyperfine model for the magnetically ordered system. The arrow label the long-range magnetic ordering temperature.
• Figure 3: (a and b) Shows ZF $\mu$SR spectra of TbV$_{6}$Sn$_{6}$ collected at various temperatures, showing clear oscillations as T$\rightarrow$T$_{C}$ (T$_{C}$ taken from heat capacity). Solid lines represent the fit as described in the text. (c and d) Shows the temperature dependence of the fit parameters relaxation rate $\lambda_{L}$, asymmetry A$_{L}$, frequency $\nu/2\pi$ and mean field at muon site B$_{int}$ extracted by fitting the zero field data collected between 1.5 and 250 K. The dotted line is a guide to the eye. The inset of Fig. 3d displays the temperature-independent longitudinal relaxation rate, $\lambda_L$, in the magnetically ordered regime, which remains finite at approximately 1 $\mu$s$^{-1}$.
• Figure 4: (a, b) ZF and 100 Oe $\mu$SR spectra of DyV$_{6}$Sn$_{6}$ at various temperatures. Solid lines are fitting results as explained in the main text. (c, d and e) Shows the temperature dependence of fit parameters relaxation rate $\lambda_1$, $\lambda_2$, total asymmetry and the inset of Fig. 4c shows temperature dependence of asymmetry paramters for ZF. The grey region marked the long-range ordering temperature from the heat capacity measurements. (4f) Shows the $\mu$SR spectra collected at various longitudinal fields ranging between 0 and 7.8 kOe at 100 K.