Quadrupole coupling constant, eqQh, of Fe3+ in several rare-earth iron garnets

Using the Mössbauer effect, values of eqQh of Fe3+ have been obtained at each of two sites in several rare-earth iron garnets. The measured values of eqQh were compared with values obtained using a point-charge lattice sum calculation. For the octahedral (a) site there was reasonable agreement between the measured and calculated values of eqQh indicating that an ionic model is reasonably valid. However, the measured values of eqQh at tetrahedral (d) sites were larger than those estimated. This difference is attributed to a small amount of covalent bonding which is also evident in the values of the (d) site internal field and isomer shift. © 1964 The American Physical Society.