Physical Review X (Dec 2017)

Weakly-Correlated Nature of Ferromagnetism in Nonsymmorphic CrO_{2} Revealed by Bulk-Sensitive Soft-X-Ray ARPES

  • F. Bisti,
  • V. A. Rogalev,
  • M. Karolak,
  • S. Paul,
  • A. Gupta,
  • T. Schmitt,
  • G. Güntherodt,
  • V. Eyert,
  • G. Sangiovanni,
  • G. Profeta,
  • V. N. Strocov

DOI
https://doi.org/10.1103/PhysRevX.7.041067
Journal volume & issue
Vol. 7, no. 4
p. 041067

Abstract

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Chromium dioxide CrO_{2} belongs to a class of materials called ferromagnetic half-metals, whose peculiar aspect is that they act as a metal in one spin orientation and as a semiconductor or insulator in the opposite one. Despite numerous experimental and theoretical studies motivated by technologically important applications of this material in spintronics, its fundamental properties such as momentum-resolved electron dispersions and the Fermi surface have so far remained experimentally inaccessible because of metastability of its surface, which instantly reduces to amorphous Cr_{2}O_{3}. In this work, we demonstrate that direct access to the native electronic structure of CrO_{2} can be achieved with soft-x-ray angle-resolved photoemission spectroscopy whose large probing depth penetrates through the Cr_{2}O_{3} layer. For the first time, the electronic dispersions and Fermi surface of CrO_{2} are measured, which are fundamental prerequisites to solve the long debate on the nature of electronic correlations in this material. Since density functional theory augmented by a relatively weak local Coulomb repulsion gives an exhaustive description of our spectroscopic data, we rule out strong-coupling theories of CrO_{2}. Crucial for the correct interpretation of our experimental data in terms of the valence-band dispersions is the understanding of a nontrivial spectral response of CrO_{2} caused by interference effects in the photoemission process originating from the nonsymmorphic space group of the rutile crystal structure of CrO_{2}.