Transition and spin dynamics at very low temperature in the pyrochlores Yb2Ti2O7 and Gd2Sn2O7

TL;DR

This study investigates the low-temperature magnetic and spin dynamics of Yb2Ti2O7 and Gd2Sn2O7 pyrochlores, revealing distinct transition behaviors and persistent spin fluctuations down to 20mK due to geometric frustration.

Contribution

It provides new insights into the contrasting low-temperature transitions and spin dynamics in two pyrochlore compounds, highlighting the role of frustration in their magnetic properties.

Findings

Gd2Sn2O7 undergoes a magnetic transition to long-range order at 1K.

Yb2Ti2O7 shows a liquid-gas-like transition at 0.24K without long-range order.

Spin fluctuations persist down to 20mK in both compounds.

Abstract

The very low temperature properties of two pyrochlore compounds, Yb2Ti2O7 and Gd2Sn2O7, were investigated using an ensemble of microscopic and bulk techniques. In both compounds, a first order transition is evidenced, as well as spin dynamics persisting down to the 20mK range. The transition however has a quite different character in the two materials: whereas that in Gd2Sn2O7$ (at 1K) is a magnetic transition towards long range order, that in Yb2Ti2O7 (at 0.24K) is reminiscent of the liquid-gas transition, in the sense that it involves a 4 orders of magnitude drop of the spin fluctuation frequency; furthermore, no long range order is observed. These unusual features we attribute to frustration of the antiferromagnetic exchange interaction in the pyrochlore lattice.