Local Electronic Structure and Dynamics of Muon-Polaron Complexes in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>Fe</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>
Martin H. Dehn, J. Kane Shenton, Donald J. Arseneau, W. A. MacFarlane, G. D. Morris, Alan Maignè, Nicola A. Spaldin, R. F. Kiefl
Abstract
We perform detailed muon spin rotation ($\ensuremath{\mu}\mathrm{SR}$) measurements in the classic antiferromagnet ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ and explain the spectra by considering dynamic population and dissociation of charge-neutral muon-polaron complexes. We show that charge-neutral muon states in ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$, despite lacking the signatures typical of charge-neutral muonium centers in nonmagnetic materials, have a significant impact on the measured $\ensuremath{\mu}\mathrm{SR}$ frequencies and relaxation rates. Our identification of such polaronic muon centers in ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ suggests that isolated hydrogen (H) impurities form analogous complexes, and that H interstitials may be a source of charge carrier density in ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$.