# Intrinsic Low-Temperature Magnetism in SmB6

## TL;DR

This study uses muon spin relaxation to distinguish intrinsic from extrinsic low-temperature magnetism in SmB6, revealing persistent magnetic fluctuations and their possible impact on surface conductivity in this topological Kondo insulator.

## Contribution

It provides new insights into the intrinsic low-energy magnetic fluctuations in SmB6 and their relation to surface conductivity, using advanced muon spin relaxation techniques.

## Key findings

- Detection of quasi-static magnetism from impurities and vacancies below 10 K
- Identification of intrinsic low-energy magnetic fluctuations at millikelvin temperatures
- Observation of a bulk magnetic excitation at 2.6 meV affecting surface conductivity

## Abstract

By means of new muon spin relaxation experiments, we disentangle extrinsic and intrinsic sources of low-temperature bulk magnetism in the candidate topological Kondo insulator (TKI) SmB6. Results on Al-flux grown SmB6 single crystals are compared to those on a large floating-zone grown ^{154}Sm^{11}B6 single crystal in which a 14 meV bulk spin exciton has been detected by inelastic neutron scattering. Below ~ 10 K we detect the gradual development of quasi-static magnetism due to rare-earth impurities and Sm vacancies. Our measurements also reveal two additional forms of intrinsic magnetism: 1) underlying low-energy (~ 100 neV) weak magnetic moment (~ 10^{-2} mu_B) fluctuations similar to those detected in the related candidate TKI YbB12 that persist down to millikelvin temperatures, and 2) magnetic fluctuations consistent with a 2.6 meV bulk magnetic excitation at zero magnetic field that appears to hinder surface conductivity above ~ 4.5 K. We discuss potential origins of the magnetism.