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.
@article{arxiv.1905.08769,
title = {Intrinsic Low-Temperature Magnetism in SmB6},
author = {S. Gheidi and K. Akintola and A. M. Cote and S. R. Dunsiger and C. Broholm and W. T. Fuhrman and S. R. Saha and J. Paglione and J. E. Sonier},
journal= {arXiv preprint arXiv:1905.08769},
year = {2019}
}