Hyperfine interaction in K2Ba[Fe(NO2)6].

Abstract

Magnetic hyperfine splitting observed in the low temperature Mössbauer spectrum of potassium barium hexanitro ferrate(II), in the absence of any external field, is attributed to the 5T2g state of the central metal atom further split into a ground 5Eg state and a first excited 5B2g state under a distorted octahedral symmetry in contrast to the earlier prediction of 1A1g ground state on the basis of room temperature Mössbauer spectral and other properties. The central iron atom is coordinated to six nitrito groups (NO2-), having an oxidation state of +2. The temperature dependence of Mössbauer spectra is explained on the basis of electronic relaxation among the spin-orbit coupled levels of the 5Eg ground state. Various kinds of electronic relaxation mechanisms have been compared to explain the proposed mechanism. The observed temperature dependent spectra with varying internal magnetic field and line width can be explained by simple spin lattice relaxation.