{\mu}SR Study of Spin Dynamics in LiY$_{1-x}$Ho$_{x}$F$_{4}$

TL;DR

This study uses zero-field {bc}SR measurements to investigate spin dynamics in LiY$_{1-x}$Ho$_{x}$F$_{4}$, revealing strong magnetic fluctuations and correlations that influence the system's behavior at low temperatures.

Contribution

The paper provides the first detailed {bc}SR analysis of LiY$_{1-x}$Ho$_{x}$F$_{4}$, combining experiments with Monte Carlo simulations to understand spin interactions and magnetic fluctuations.

Findings

F-{bc}-F oscillations do not evolve into Lorentzian decay as expected.

Strong magnetic fluctuations are present at low temperatures.

Numerical calculations suggest correlations significantly affect spin dynamics.

Abstract

We present zero-field {\mu}SR measurements for LiY$_{1-x}$Ho$_{x}$F$_{4}$ samples with x = 0.0017, 0.0085, 0.0406, and 0.0855. We characterize the dynamics associated with the formation of the (F-{\mu}-F)$^{-1}$ complex by comparing our data to Monte Carlo simulations to determine the concentration range over which the spin dynamics are determined primarily by the Ho$^{3+}$-{\mu} interaction rather than the F-{\mu} interaction. Simulations show that F-{\mu}-F oscillations should evolve into a Lorentzian Kubo-Toyabe decay for an increasing static magnetic field distribution {\Gamma} (i.e., increasing x), but the data do not show this behavior, consistent with the recently reported existence of strong magnetic fluctuations in this system at low temperatures. Anisotropy in the field distribution is shown to cause small errors of order 10% from behavior predicted for an isotropic distribution. Finally, numerical calculations show that values of {\Gamma} calculated in the single ion limit greatly exceed the values extracted from curve fits, suggesting that strong correlations play an important role in this system.