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Magnetic Order and Spin Dynamics in Ferroelectric HoMnO$_{3}$

O. P. Vajk·M. Kenzelmann·J. W. Lynn·S. B. Kim·S. -W. Cheong
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Abstract

Hexagonal HoMnO$_{3}$ is a frustrated antiferromagnet (T$_{N}$=72 K) ferroelectric (T$_{C}$=875 K) in which these two order parameters are coupled. Our neutron measurements of the spin wave dispersion for the S=2 Mn$^{3+}$ on the layered triangular lattice are well described by a two-dimensional nearest-neighbor Heisenberg exchange J=2.44 meV, and an anisotropy $D$ that is 0.093 meV above the spin reorientation transition at 40 K, and 0.126 meV below. For $H\parallel c$ the magnetic structures and phase diagram have been determined, and reveal additional transitions below 8 K where the ferroelectrically displaced Ho$^{3+}$ ions are ordered magnetically.

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O. P. Vajk, M. Kenzelmann, J. W. Lynn, S. B. Kim, S. -W. Cheong. 2005-01-31. Magnetic Order and Spin Dynamics in Ferroelectric HoMnO$_{3}$. https://doi.org/10.1103/physrevlett.94.087601

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