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 ⁵T_2g state of the central metal atom further split into a ground ⁵E_g state and a first excited ⁵B_2g state under a distorted octahedral symmetry in contrast to the earlier prediction of ¹A_1g ground state on the basis of room temperature Mössbauer spectral and other properties. The central iron atom is co-ordianted 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 ⁵E_g 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.