Magnons and magnetodielectric effects in CoCr^sub 2^O^sub 4^: Raman scattering studies

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 multiferroi...

Full description

Saved in:
Bibliographic Details
Published in:Physical review. B 2017-05, Vol.95 (17), p.174413
Main Authors: Sethi, A, Byrum, T, McAuliffe, R D, Gleason, S L, Slimak, J E, Shoemaker, D P, Cooper, S L
Format: Article
Language:English
Subjects:
Curie temperature
Dielectric strength
Ferrimagnetism
Ferroelectric materials
Ferroelectricity
Inelastic scattering
Light scattering
Magnetic anisotropy
Magnetic permeability
Magnetic variations
Magnons
Multiferroic materials
Phonons
Pressure dependence
Raman spectra
Symmetry
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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 = 94 K) of CoCr2O4 we observe a ω ~ 16 cm−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.
ISSN:2469-9950
2469-9969