Quadrupole Coupling Constant,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mfrac><mml:mrow><mml:mi>eqQ</mml:mi></mml:mrow><mml:mrow><mml:mi>h</mml:mi></mml:mrow></mml:mfrac></mml:math>, of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">Fe</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>in Several Rare-Earth Iron Garnets

Abstract

Using the M\"ossbauer effect, values of $\frac{\mathrm{eqQ}}{h}$ of ${\mathrm{Fe}}^{3+}$ have been obtained at each of two sites in several rare-earth iron garnets. The measured values of $\frac{\mathrm{eqQ}}{h}$ 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 $\frac{\mathrm{eqQ}}{h}$ indicating that an ionic model is reasonably valid. However, the measured values of $\frac{\mathrm{eqQ}}{h}$ 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.