Pseudodipolar and exchange broadening of NMR lines in GaP and GaAs

Abstract

The pseudodipolar and exchange constants are measured for GaP and GaAs using pulsed NMR. The constants for GaP are derived from measurements of the second moment of $^{31}\mathrm{P}$ free induction decays (FID). A line-shape theory is used to eliminate quadrupolar contributions to the second moments of FID's in GaAs and simplify measurement of the coupling constants in that material. Results are discussed with reference to theoretical predictions based on an extension of the bond-orbital model (BOM) of tetrahedrally coordinated solids. A linear relationship between the exchange coupling constant and the static dielectric constant is found for the series GaP, GaAs, GaSb, as predicted by the BOM.