An anisotropic local modification of crystal field levels in Pr-based pyrochlores: a muon-induced effect modelled using density functional theory

TL;DR

This study investigates how muons induce local distortions in Pr-based pyrochlores, affecting their magnetic properties, by combining muon spin relaxation measurements with density functional theory modeling to explain hyperfine enhancements.

Contribution

The paper introduces a model explaining muon-induced anisotropic crystal field modifications in Pr pyrochlores using DFT, linking local distortions to observed magnetic effects.

Findings

Muon spin relaxation indicates static magnetic moments grow at low temperatures.

Density functional theory shows muons cause anisotropic distortions near Pr ions.

Hyperfine enhancement explains the larger-than-expected magnetic moments.

Abstract

Muon spin relaxation measurements on some quantum spin ice candidate materials, the insulating pyrochlores Pr2B2O7 (B = Sn, Zr, Hf), have been performed for temperatures in the range 0.05-280 K. The results are indicative of a static distribution of magnetic moments which appears to grow on cooling and whose size at low temperatures is significantly larger than that expected for Pr nuclear moments. Using density functional theory we show how this effect can be explained via a hyperfine enhancement arising from a splitting of the non-Kramers doublet ground states on Pr ions close to the muon which itself causes a highly anisotropic distortion field. We provide a quantitative relationship between this effect and the measured temperature dependence of the muon relaxation and discuss the relevance of these observations to muon experiments in other frustrated magnetic materials.