Ferromagnetic Resonance of the Weak Ferromagnet Sr$_2$IrO$_4$

ORAL

Abstract

We derive a pseudospin model for the strongly spin-orbit coupled 5$d$ oxide Sr$_2$IrO$_4$ that is based on a standard $t/U$ expansion and Slater's theory of atomic multiplets. Using this model, we use linear spin-wave theory to evaluate the material's spin wave spectrum and address the influence of quantum fluctuation on the saturation magnetization. We find that the ferromagnetic resonance (FMR) frequency has an unusual square root dependence on magentic field, with a prefactor related to the strength of the exchange coupling between $j=1/2$ pseudospins. FMR can thus be used as an alternative probe of the nontrivial magnetism of Sr$_2$IrO$_4$.

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Authors

  • Hua Chen

    • University of Texas at Austin
    • Department of Physics, The University of Texas at Austin, Austin, TX, 78712
    • The University of Texas at Austin

  • Allan MacDonald

    • The University of Texas at Austin
    • Department of Physics, University of Texas at Austin, Austin, Texas 78712-1081, USA
    • Department of Physics, The University of Texas at Austin, Austin, TX, 78712
    • Department of Physics, University of Texas at Austin
    • University of Texas at Austin
    • University of Texas at Austin, Austin, Texas 78712, USA
    • UT Austin
    • Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA