Infrared-active excitations related to Ho3+ ligand-field splitting at the commensurate-incommensurate magnetic phase transition in HoMn2O5

A. A. Sirenko, S. M. O'Malley, K. H. Ahn, S. Park, G. L. Carr, S. W. Cheong

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13 Scopus citations

Abstract

Linearly polarized spectra of far-infrared (IR) transmission in HoMn2 O5 multiferroic single crystals have been studied in the frequency range between 8.5 and 105 cm-1 and for temperatures between 5 and 300 K. Polarization of IR-active excitations depends on the crystallographic directions in HoMn2 O5 and is sensitive to the magnetic phase transitions. We attribute some of the infrared-active excitations to electric-dipole transitions between ligand-field (LF) split states of Ho3+ ions. For light polarization along crystalline b axis, the oscillator strength of electric dipoles at low frequencies (10.5, 13, and 18 cm-1) changes significantly at the commensurate-incommensurate antiferromagnetic phase transition at T3 =19 K. This effect shows a strong correlation with the pronounced steps of the b -directional static dielectric function. We propose that the LF on Ho3+ connects the magnetism and dielectric properties of this compound through coupling with the Mn spin structure. We comment on the possibility for composite excitations of magnons and excited LF states.

Original languageEnglish (US)
Article number174405
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume78
Issue number17
DOIs
StatePublished - Nov 6 2008

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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