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Compensation temperatures and exchange bias in La1.5Ca0.5CoIrO6

L. T. Coutrim, E. M. Bittar, F. Stavale, F. Garcia, E. Baggio-Saitovitch, M. Abbate, R. J. O. Mossanek, H. P. Martins, D. Tobia, P. G. Pagliuso, and L. Bufaiçal
Phys. Rev. B 93, 174406 – Published 9 May 2016
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  • INTRODUCTION
  • EXPERIMENTAL DETAILS
  • RESULTS AND DISCUSSION
  • CONCLUSIONS AND OUTLOOK
  • ACKNOWLEDGMENTS
    • Supplemental Material
    References

    Abstract

    We report on the study of magnetic properties of the La1.5Ca0.5CoIrO6 double perovskite. Via ac magnetic susceptibility we have observed evidence of weak ferromagnetism and reentrant spin glass behavior on an antiferromagnetic matrix. Regarding the magnetic behavior as a function of temperature, we have found that the material displays up to three inversions of its magnetization, depending on the appropriate choice of the applied magnetic field. At low temperature, the material exhibits exchange bias effect when it is cooled in the presence of a magnetic field. Also, our results indicate that this effect may be observed even when the system is cooled at zero field. Supported by other measurements and also by electronic structure calculations, we discuss the magnetic reversals and spontaneous exchange bias effect in terms of magnetic phase separation and magnetic frustration of Ir4+ ions located between the antiferromagnetically coupled Co ions.

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    • Received 17 December 2015
    • Revised 11 April 2016

    DOI:https://doi.org/10.1103/PhysRevB.93.174406

    ©2016 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Exchange biasFrustrated magnetism
    1. Physical Systems
    IridatesSpin glasses
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    L. T. Coutrim1, E. M. Bittar2, F. Stavale2, F. Garcia2, E. Baggio-Saitovitch2, M. Abbate3, R. J. O. Mossanek3, H. P. Martins3, D. Tobia4, P. G. Pagliuso4, and L. Bufaiçal1,*

    • 1Instituto de Física, Universidade Federal de Goiás, 74001-970, Goiânia, GO, Brazil
    • 2Centro Brasileiro de Pesquisas Físicas, 22290-180, Rio de Janeiro, RJ, Brazil
    • 3Universidade Federal do Paraná, 19044, 81531-990 Curitiba, PR, Brazil
    • 4Instituto de Física “Gleb Wataghin”, UNICAMP, 13083-859, Campinas, SP, Brazil

    • *lbufaical@ufg.br

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    Issue

    Vol. 93, Iss. 17 — 1 May 2016

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    Images

    • Figure 1
      Figure 1

      (a) XPS survey spectra for La1.5Ca0.5CoIrO6. All elements observed in the sample are indicated. (b) High-resolution Co 2p region for several Ca doping levels and the corresponding peak components fitting using the Shirley background and two Lorentzian-Gaussian peaks for Co2+ and Co3+ cations component. (c) The corresponding valence-band photoemission features and the main peaks indicated by line 1 and line 2, related to the high-spin state of the Co3+ cations.

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    • Figure 2
      Figure 2

      (a) ZFC and FC magnetization as a function of T for La1.5Ca0.5CoIrO6 at Hdc=500 Oe. The inset shows the magnified view of the AFM and FM transitions of Co ion. (b) ZFC magnetization as a function of T at Hdc=200 Oe (solid circle), Hdc=500 Oe (solid square), and Hdc=1000 Oe (solid line). The inset shows the Hdc=500 Oe FC curve at low-T.

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    • Figure 3
      Figure 3

      (a) χac′ and χac′′ as a function of T at various frequencies. The inset shows Tf as a function of frequency for Hdc=0 and 500 Oe, obtained from χac′. The lines are best fits to the power law Tf=Tsg[1+(τ0f)1/zν)]. (b) χac′ and χac′′ vs T at f=1000 Hz for various Hdc. Inset shows Tf for different applied Hdc.

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    • Figure 4
      Figure 4

      Temperature-field phase diagram showing the Néel (TN), critical (TC), and freezing (Tf) temperatures of La1.5Ca0.5CoIrO6. The lines are guides for the eye.

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    • Figure 5
      Figure 5

      (a) ZFC M(H) loops at 5 and 15 K. The inset shows a magnified view of the initial magnetization values at zero field. (b) ZFC M(H) loops at 2 K performed as 0→4T→−4T→4 T and 0→−4T→4T→−4 T. (c) FM + SG contributions to the M(H) loop at T=5 K. The doted lines are guides for the eye. The inset shows the original curve and the linear AFM contribution (see text).

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    • Figure 6
      Figure 6

      (a) HZEB and HC evolution with T. The inset shows a magnified view of the low-T anomaly on HC. The lines are guides for the eye. (b) MR dependency with T.

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    • Figure 7
      Figure 7

      (a) M(H) loop at 5 K after cooling the system with HFC=3 T. The inset shows the deconvolute curve (see text). (b) Magnified view of the curves measured at 2 K after the sample being field cooled with HFC±3 T. (c) HCEB and HC evolution with T.

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    • Figure 8
      Figure 8

      Training effect of CEB at 2 K. The inset shows HCEB as a function of the hystereis number (n). The solid line represents the fitting of the experimental data to Eq. (6).

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