Quantum states of muons in fluorides

TL;DR

This paper demonstrates that electronic-structure calculations can accurately determine muon implantation sites and perturbations in fluorides, improving the reliability of muon-spin relaxation measurements of magnetism.

Contribution

It introduces a systematic approach using electronic-structure calculations to address muon site identification and perturbation effects in bc SR studies of fluorides.

Findings

Diamagnetic muons cause significant short-range distortions in ionic insulators.

The F--bc--F complex acts as an exotic molecule-in-a-crystal defect.

Quantified distortions can lead to systematic errors in magnetic moment measurements.

Abstract

Muon-spin relaxation (\mu SR) is a sensitive probe of magnetism, but its utility can be severely limited by the lack of knowledge of the muon implantation site and the extent to which the muon perturbs its host. We demonstrate systematically that these problems can be addressed accurately using electronic-structure calculations. We show that diamagnetic muons introduce significant short-ranged distortions in ionic insulators that would lead to systematic errors on magnetic moments determined by \mu SR, and quantify these. The F--\mu--F complex formed by muons in many fluorides can be understood as an exotic molecule-in-a-crystal defect with a zero-point energy larger than that of any naturally-occurring triatomic molecule.