Spin–lattice coupling in iron jarosite

Spin–lattice coupling in iron jarosite

We have studied the magnetoelectric coupling of the frustrated triangular antiferromagnet iron jarosite using Raman spectroscopy, dielectric measurements and specific heat. Temperature dependent capacitance measurements show an anomaly in the dielectric constant at TN. Specific heat data indicate th...

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Bibliographic Details
Published in:Journal of solid state chemistry Vol. 195; pp. 50 - 54
Main Authors: Buurma, A.J.C., Handayani, I.P., Mufti, N., Blake, G.R., van Loosdrecht, P.H.M., Palstra, T.T.M.
Format: Journal Article
Language:English
Published: United States Elsevier Inc 01-11-2012
Subjects:
ANTIFERROMAGNETISM
BRILLOUIN ZONES
COUPLING
DIELECTRIC MATERIALS
DIPOLE MOMENTS
FREE ENERGY
Frustrated triangular antiferromagnet
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
IRON
Jarosite
LIGANDS
MAGNETIC FIELDS
MAGNETIC PROPERTIES
MATERIALS SCIENCE
PERMITTIVITY
Phonon mode
POTASSIUM
RAMAN SPECTROSCOPY
SPECIFIC HEAT
TEMPERATURE DEPENDENCE
Frustrated triangular antiferromagnet
Jarosite
Phonon mode
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Summary:We have studied the magnetoelectric coupling of the frustrated triangular antiferromagnet iron jarosite using Raman spectroscopy, dielectric measurements and specific heat. Temperature dependent capacitance measurements show an anomaly in the dielectric constant at TN. Specific heat data indicate the presence of a low frequency Einstein mode at low temperature. Raman spectroscopy confirms the presence of a new mode below TN that can be attributed to folding of the Brillouin zone. This mode shifts and sharpens below TN. We evaluate the strength of the magnetoelectric coupling using the symmetry unrestricted biquadratic magnetoelectric terms in the free energy. Sketch of two connected triangles formed by Fe3+ spins (red arrows) in the hexagonal basal plane of potassium iron jarosite. An applied magnetic field (H) below the antiferromagnetic ordering temperature induces shifts of the hydroxy ligands, giving rise to local electrical dipole moments (blue arrows). These electric displacements cancel out in pairwise fashion by symmetry. Ligand shifts are confined to the plane and shown by shadowing. [Display omitted] ► Evidence has been found for spin–lattice coupling in iron jarosite. ► A new optical Raman mode appears below TN and shifts with temperature. ► The magnetodielectric coupling is mediated by superexchange. ► Symmetry of Kagome magnetic lattice causes local electrical dipole moments to cancel.
ISSN:0022-4596
1095-726X
DOI:10.1016/j.jssc.2012.03.011