Low energy magnetic excitations in the spin-orbital Mott insulator Sr$_2$IrO$_4$

S. Bahr; A. Alfonsov; G. Jackeli; G. Khaliullin; A. Matsumoto; T. Takayama; H. Takagi; B. Büchner; V. Kataev

doi:10.1103/PhysRevB.89.180401

Low energy magnetic excitations in the spin-orbital Mott insulator Sr$_2$IrO$_4$

Strongly Correlated Electrons 2015-06-18 v2

Authors: S. Bahr , A. Alfonsov , G. Jackeli , G. Khaliullin , A. Matsumoto , T. Takayama , H. Takagi , B. Büchner , V. Kataev

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Abstract

We report a high-field electron spin resonance study in the sub-THz frequency domain of a single crystal of Sr $_2$ IrO $_4$ that has been recently proposed as a prototypical spin-orbital Mott insulator. In the antiferromagnetically (AFM) ordered state with noncollinear spin structure that occurs in this material at $T_{\rm N} \approx 240$ K we observe both the "low" frequency mode due to the precession of weak ferromagnetic moments arising from a spin canting, and the "high" frequency modes due to the precession of the AFM sublattices. Surprisingly, the energy gap for the AFM excitations appears to be very small, amounting to 0.83 meV only. This suggests a rather isotropic Heisenberg dynamics of interacting Ir $^{4+}$ effective spins despite the spin-orbital entanglement in the ground state.

Keywords

spin-orbital Mott insulator electron spin resonance Sr2IrO4 antiferromagnetic excitations spin canting Heisenberg dynamics

Cite

@article{arxiv.1312.4847,
  title  = {Low energy magnetic excitations in the spin-orbital Mott insulator Sr$_2$IrO$_4$},
  author = {S. Bahr and A. Alfonsov and G. Jackeli and G. Khaliullin and A. Matsumoto and T. Takayama and H. Takagi and B. Büchner and V. Kataev},
  journal= {arXiv preprint arXiv:1312.4847},
  year   = {2015}
}

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revised version

Low energy magnetic excitations in the spin-orbital Mott insulator Sr$_2$IrO$_4$

Abstract

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