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Surface excitations relaxation in the Kondo insulator Sm1−xGdxB6

J. C. Souza1,2,*, M. König2, M. V. Ale Crivillero2, M. O. Malcolms1, R. R. Urbano1, Z. Fisk3, P. F. S. Rosa4, P. G. Pagliuso1, S. Wirth2 et al.

J. Sichelschmidt2

  • 1Instituto de Física “Gleb Wataghin”, UNICAMP, 13083-859 Campinas, São Paulo, Brazil
  • 2Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
  • 3Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
  • 4Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

  • *jcsouza@ifi.unicamp.br
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Phys. Rev. Research 3, 033016 – Published 2 July, 2021

DOI: https://doi.org/10.1103/PhysRevResearch.3.033016

Abstract

The interplay between nontrivial topological states of matter and strong electronic correlations is one of the most compelling open questions in condensed matter physics. Due to experimental challenges, there is an increasing desire to find more microscopic techniques to complement the results of more traditional experiments. In this work, we locally explore the Kondo insulator Sm1−xGdxB6 by means of electron spin resonance (ESR) of Gd3+ ions at low temperatures. Our analysis reveals that the Gd3+ ESR line shape shows an anomalous evolution as a function of temperature, wherein for highly dilute samples (x≈0.0002) the Gd3+ ESR line shape changes from a localized ESR local moment character to a diffusive-like character. Upon manipulating the sample surface with a focused ion beam we demonstrate, in combination with electrical resistivity measurements, that the localized character of the Gd3+ ESR line shape is recovered by increasing the penetration of the microwave in the sample. This provides compelling evidence for the contribution of surface or near-surface excitations to the relaxation mechanism in the Gd3+ spin dynamics. Our work brings new insights into the importance of nontrivial surface excitations in ESR, opening new routes to be explored both theoretically and experimentally.

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Phys. Rev. Research 3, 033016– Published 2 July, 2021
  • Received 13 April 2021
  • Revised 8 June 2021
  • Accepted 9 June 2021
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