Bulk rutile RuO$_{2}$ has long been considered a Pauli paramagnet. Here we report that RuO$_{2}$ exhibits a hitherto undetected lattice distortion below approximately 900 K. The distortion is accompanied by antiferromagnetic order up to at least 300 K with a small room temperature magnetic moment of approximately 0.05 $\mu$ B as evidenced by polarized neutron diffraction. Density functional theory plus U (DFT$+$U) calculations indicate that antiferromagnetism is favored even for small values of the Hubbard U of the order of 1 eV. The antiferromagnetism may be traced to a Fermi surface instability, lifting the band degeneracy imposed by the rutile crystal field. The combination of high N\'{e}el temperature and small itinerant moments make RuO$_{2}$ unique among ruthenate compounds and among oxide materials in general.
*This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.
–
Authors
Paul Snijders
Oak Ridge National Lab
Oak Ridge National Laboratory
Tom Berlijn
Oak Ridge National Laboratory
Olivier Delaire
Duke University
Haidong Zhou
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
University of Tennessee
University of Tennessee, Knoxville
University of Tennessee,Knoxville, TN 37996, USA
University of Tennessee, Knoxville, National High Magnetic Field Laboratory
Thomas Maier
Oak Ridge National Laboratory
Computer Science and Mathematics Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6494, USA
Oak Ridge National Lab
Oak Ridge National Lab.
Huibo Cao
Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TK 37831, USA
Oak Ridge National Laboratory
Quantum Condensed Matter Division, Oak Ridge National Laboratory
Songxue Chi
Oak Ridge National Laboratory
Oak Ridge Natl Lab
Quantum Condensed Matter Division, Oak Ridge National Laboratory
Masaaki Matsuda
Oak Ridge National Lab
Quantum Condensed Matter Division, Oak Ridge National Laboratory
