Magnons and magnetodielectric effects in CoCr2 O4: Raman scattering studies

A. Sethi, T. Byrum, R. D. McAuliffe, S. L. Gleason, J. E. Slimak, D. P. Shoemaker, S. L. Cooper

Research output: Contribution to journalArticlepeer-review


Magnetoelectric materials have generated wide technological and scientific interest because of the rich phenomena these materials exhibit, including the coexistence of magnetic and ferroelectric orders, magnetodielectric behavior, and exotic hybrid excitations such as electromagnons. The multiferroic spinel material CoCr2O4 is a particularly interesting example of a multiferroic material, because evidence for magnetoelectric behavior in the ferrimagnetic phase seems to conflict with traditional noncollinear-spin-driven mechanisms for inducing a macroscopic polarization. With the overall goal of clarifying the magnetodielectric behavior previously reported below TC in CoCr2O4, in this paper we report an inelastic light scattering study of the magnon and phonon spectrum of CoCr2O4 as simultaneous functions of temperature, pressure, and magnetic field. Below the Curie temperature (TC=94K) of CoCr2O4 we observe a ω∼16cm-1 q=0 magnon having T1g-symmetry, which has the transformation properties of an axial vector. The anomalously large Raman intensity of the T1g-symmetry magnon is characteristic of materials with a large magneto-optical response and likely arises from large magnetic fluctuations that strongly modulate the dielectric response in CoCr2O4. The Raman susceptibility of the T1g-symmetry magnon exhibits a strong magnetic-field dependence that is consistent with the magnetodielectric response observed in CoCr2O4, suggesting that magnetodielectric behavior in CoCr2O4 primarily arises from the field-dependent suppression of magnetic fluctuations that are strongly coupled to long-wavelength phonons. Increasing the magnetic anisotropy in CoCr2O4 with applied pressure decreases the magnetic-field dependence of the T1g-symmetry magnon Raman susceptibility, suggesting that strain can be used to control the magnetodielectric response in CoCr2O4.

Original languageEnglish (US)
Article number174413
JournalPhysical Review B
Issue number17
StatePublished - May 9 2017

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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