Muon diffusion and electronic magnetism in Y$_2$Ti$_2$O$_7$

TL;DR

This study uses muon spin relaxation to investigate magnetic and diffusion properties in Y$_2$Ti$_2$O$_7$, revealing temperature-dependent muon diffusion and magnetic trapping phenomena linked to Ti$^{3+}$ defects.

Contribution

It provides new insights into muon diffusion and magnetic trapping mechanisms in Y$_2$Ti$_2$O$_7$, highlighting their relevance to spin dynamics in pyrochlore materials.

Findings

Muon diffusion becomes incoherent below 40 K.

Strong electronic magnetic signals linked to Ti$^{3+}$ defects.

Temperature-dependent muon trapping and release observed.

Abstract

We report a $\mu$SR study in a Y$_2$Ti$_2$O$_7$ single crystal. We observe slow local field fluctuations at low temperature which become faster as the temperature is increased. Our analysis suggests that muon diffusion is present in this system and becomes small below 40 K and therefore incoherent. A surprisingly strong electronic magnetic signal is observed with features typical for muons thermally diffusing towards magnetic traps below $\approx 100$ K and released from them above this temperature. We attribute the traps to Ti$^{3+}$ defects in the diluted limit. Our observations are highly relevant to the persistent spin dynamics debate on $R_2$Ti$_2$O$_7$ pyrochlores and their crystal quality.