Evidence of the Plaquette Structure of Fe_1+xTe Iron Telluride: Mössbauer Spectroscopy Study

Abstract

Single‐crystalline Fe1+xTe iron telluride with off‐stoichiometric iron has been synthesized by the Bridgman method. The X‐ray diffraction and wave‐length‐dispersive X‐ray electron‐probe microanalysis characterization have shown Fe1.125Te stoichiometry of the samples. Spin‐polarized ab initio calculations of the electric field gradients around interstitial iron atoms for Fe1.125Te have shown that in the first and second coordination rings around interstitial iron, the spin and electron densities are strongly perturbed against the stoichiometric ones. Together with the interstitial iron this gives rise to three kinds of iron centers making up a round‐corner plaquette. The room‐temperature Mössbauer spectra measured at different incidence angles of gamma‐radiation are satisfactorily fitted utilizing the hyperfine parameters, calculated within the plaquette model. The low‐temperature data are well described with the assumption of an incommensurate collinear spin density wave (SDW) phase, showing consistency with neutron scattering data for the Fe1.125Te system.