Determination of the Gradient-Elastic Tensors forAIIIBVCompounds Using Nuclear Acoustic Resonance

Abstract

Acoustic waves in crystalline solids can couple energy to nuclear spin systems via the nuclear electric quadrupole interaction. For a known quadrupole moment, measurement of the acoustic attenuation due to this interaction allows the determination of the components of the fourth-order tensor connecting electric field gradients to elastic strains. By the use of nuclear acoustic resonance at 300°K, the magnitudes and relative signs of the gradient-elastic tensor components have been determined for type ${\mathrm{A}}^{\mathrm{III}}$ ${\mathrm{B}}^{\mathrm{V}}$ semiconducting single crystals at the $A$ and $B$ nuclear positions in InAs, InSb, GaAs, and GaSb and at the $B$ nuclear position in AlSb. The experimental error is ±6% in the measured product of quadrupole moment and gradient-elastic tensor component. Ionic contributions to the electric field gradients alone do not explain the relative signs and magnitudes of the components. A physical model is proposed to separate the ionic and covalent contributions to the measured gradient-elastic tensor components. This model predicts the ratio of the ionic contributions to the tensor components at the same nuclear positions in two different compounds and in the same compounds. Such a model can be used to compare the several sets of effective ionic charges that have been proposed for these compounds. The ionic contributions found from this model have magnitudes that can be explained by antishielding coefficients smaller than 220. The covalent contributions at $A$ and $B$ nuclear positions have different magnitudes and different signs.