Low temperature spin fluctuations in geometrically frustrated Yb3Ga5O12

TL;DR

This study investigates low temperature spin fluctuations in the geometrically frustrated garnet Yb3Ga5O12, revealing persistent dynamic correlations without static order and identifying phonon-driven relaxation processes across a broad temperature range.

Contribution

It provides detailed measurements of spin dynamics and relaxation processes in Yb3Ga5O12 down to millikelvin temperatures, highlighting the absence of static magnetic order despite short-range correlations.

Findings

No static magnetic order below 54 mK.

Spin fluctuation frequency saturates at 3 x 10^9 s^-1 near 0 K.

Phonon-driven relaxation processes observed up to 300 K.

Abstract

In the garnet structure compound Yb3Ga5O12, the Yb3+ ions (ground state effective spin S' = 1/2) are situated on two interpenetrating corner sharing triangular sublattices such that frustrated magnetic interactions are possible. Previous specific heat measurements evidenced the development of short range magnetic correlations below 0.5K and a lambda-transition at 54mK (Filippi et al. J. Phys. C: Solid State Physics 13 (1980) 1277). From 170-Yb M"ossbauer spectroscopy measurements down to 36mK, we find there is no static magnetic order at temperatures below that of the lambda-transition. Below 0.3K, the fluctuation frequency of the short range correlated Yb3+ moments progressively slows down and as the temperature tends to 0, the frequency tends to a quasi-saturated value of 3 x 10^9 s^-1. We also examined the Yb3+ paramagnetic relaxation rates up to 300K using 172-Yb perturbed angular correlation measurements: they evidence phonon driven processes.