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X-ray absorption and x-ray magnetic dichroism study on Ca3CoRhO6 and Ca3FeRhO6

T. Burnus, Z. Hu, Hua Wu, J. C. Cezar, S. Niitaka, H. Takagi, C. F. Chang, N. B. Brookes, H.-J. Lin, L. Y. Jang, A. Tanaka, K. S. Liang, C. T. Chen, and L. H. Tjeng
Phys. Rev. B 77, 205111 – Published 14 May 2008
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  • INTRODUCTION
  • EXPERIMENT
  • X-RAY ABSORPTION SPECTROSCOPY AND…
  • X-RAY MAGNETIC CIRCULAR DICHROISM AND…
  • STABILITY OF THE d0d2 STATE
  • CONCLUSION
  • ACKNOWLEDGEMENTS
    • References

    Abstract

    By using x-ray absorption spectroscopy at the Rh L2,3, Co L2,3, and Fe L2,3 edges, we find a valence state of Co2+/Rh4+ in Ca3CoRhO6 and of Fe3+/Rh3+ in Ca3FeRhO6. X-ray magnetic circular dichroism spectroscopy at the Co L2,3 edge of Ca3CoRhO6 reveals a giant orbital moment of about 1.7μB, which can be attributed to the occupation of the minority-spin d0d2 orbital state of the high-spin Co2+ (3d7) ions in trigonal prismatic coordination. This active role of the spin-orbit coupling explains the strong magnetocrystalline anisotropy and Ising-type magnetism of Ca3CoRhO6.

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    • Received 3 March 2008

    DOI:https://doi.org/10.1103/PhysRevB.77.205111

    ©2008 American Physical Society

    Authors & Affiliations

    T. Burnus1, Z. Hu1, Hua Wu1, J. C. Cezar2, S. Niitaka3,4, H. Takagi3,4,5, C. F. Chang1, N. B. Brookes2, H.-J. Lin6, L. Y. Jang6, A. Tanaka7, K. S. Liang6, C. T. Chen6, and L. H. Tjeng1

    • 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
    • 2European Synchrotron Radiation Facility, Boîte Postale 220, 38043 Grenoble, France
    • 3Institute of Physical and Chemical Research, RIKEN, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan
    • 4CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
    • 5Department of Advanced Materials Science, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
    • 6National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30077, Taiwan
    • 7Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan

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    Issue

    Vol. 77, Iss. 20 — 15 May 2008

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    Images

    • Figure 1
      Figure 1
      The Rh L2,3 XAS spectra of Ca3CoRhO6 and Ca3FeRhO6 and a schematic energy level diagram for Rh3+ 4d6 and Rh4+ 4d5 configurations in octahedral symmetry.Reuse & Permissions
    • Figure 2
      Figure 2
      (Color online) Experimental XAS spectra at the Fe L2,3 edge of (a) Fe2O3 (Fe3+), (g) Ca3FeRhO6, and (j) FeO (Fe2+), which was taken from Park (Ref. 29), together with simulated [(b) and (c)] spectra in Oh, (d) spherical, and [(e) and (f)] D3h symmetry for Fe3+ and simulated spectra in (h) D3h and (i) Oh symmetry for Fe2+. The simulated spectra have been broadend by a Gaussian with a HWHM of 0.2 eV and Lorentzian with a HWHM of 0.3 eV.Reuse & Permissions
    • Figure 3
      Figure 3
      The Co L2,3 spectra of (a) Ca3Co2O6 (Co3+), (b) CoO (Co2+), and (c) Ca3CoRhO6. The simulated spectra of high-spin Co2+ (3d7) in trigonal prismatic symmetry are shown in (d) for d0d2 and in (e) for d2d−2 minority-spin orbital occupations.Reuse & Permissions
    • Figure 4
      Figure 4
      Scheme of the two possible 3d occupations for a high-spin Co2+ ion in trigonal prismatic symmetry, ignoring the five up spins. (a) The d0d2 minority-spin occupation allows for a large orbital magnetic moment, whereas (b) for d2d−2 the orbital moment vanishes.Reuse & Permissions
    • Figure 5
      Figure 5
      (Color online) (a) Measured soft x-ray absorption spectra with parallel (μ+, red dotted curve) and antiparallel (μ−, black solid curve) alignment between photon spin and magnetic field, together with their difference (XMCD) spectrum (μ+−μ−, blue dashed curve); simulated XMCD spectra for (b) d0d2 (olive curve) and (c) d2d−2 (magenta curve) minority-spin occupation of the high-spin Co2+.Reuse & Permissions
    • Figure 6
      Figure 6
      (Color online) Top panel: Occupation number of the d0, d2, and d−2 orbitals as a function of the d0−d±2 splitting Δ02 [Fig. 4b]. Middle panel: Orbital and spin moments (morb and mspin) as function of Δ02. Bottom panel: J(J+1), L(L+1), and S(S+1) as a function of Δ02.Reuse & Permissions
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