Raman scattering and far-infrared studies of the vanadium dihalides with layered structure

Bauhofer, W; Guntherodt, G; Anastassakis, E; Frey, A; Benedek, G

dc.contributor.author	Bauhofer, W	en
dc.contributor.author	Guntherodt, G	en
dc.contributor.author	Anastassakis, E	en
dc.contributor.author	Frey, A	en
dc.contributor.author	Benedek, G	en
dc.date.accessioned	2014-03-01T01:38:14Z
dc.date.available	2014-03-01T01:38:14Z
dc.date.issued	1980	en
dc.identifier.issn	01631829	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/21965
dc.title	Raman scattering and far-infrared studies of the vanadium dihalides with layered structure	en
heal.type	journalArticle	en
heal.identifier.primary	10.1103/PhysRevB.22.5873	en
heal.identifier.secondary	http://dx.doi.org/10.1103/PhysRevB.22.5873	en
heal.publicationDate	1980	en
heal.abstract	The vanadium dihalides with layered structure, VCl2, VBr2, and VI2, have been investigated by Raman and infrared spectroscopy. A compilation of the measured optical frequencies is given. The new lines appearing in the Raman spectrum of VI2 below its Néel temperature TN are attributed to zone-boundary-phonon Raman scattering induced by Bragg scattering from the spin superstructure. We discuss the symmetry properties and selection rules for the proposed spin-dependent electron-phonon coupling mechanism due to a phonon modulation of the exchange interaction. The measured two-phonon absorption spectra of the three materials show a shift to lower frequencies with respect to the calculated two-phonon density of states. Some possible reasons for this unusually large shift are discussed. The Raman spectra of VCl2 and VBr2 show additional features at low temperature, different from the sharp lines observed in VI2 below TN. This additional scattering is also shifted to lower frequencies compared to the calculated one-phonon density of states. We explain the appearance of the additional Raman scattering by a spin-phonon coupling via the exchange modulation mechanism, whereas the shift in the Raman spectra should be due to a self-energy renormalization by the coupling mechanism. © 1980 The American Physical Society.	en
heal.journalName	Physical Review B	en
dc.identifier.doi	10.1103/PhysRevB.22.5873	en
dc.identifier.volume	22	en
dc.identifier.issue	12	en
dc.identifier.spage	5873	en
dc.identifier.epage	5886	en