Electrically Induced Nuclear Quadrupole Spin Transitions in a GaAs Single Crystal

The direct induction of nuclear $E2\mathrm{}$ spin transitions in a gallium arsenide single crystal by application of an external oscillatory electric field has been previously reported by some of the authors. This paper gives the results of a further investigation of the same phenomenon. Theoretical expressions are given for the equilibrium nuclear magnetization in a crystalline lattice under the combined influence of a static magnetic field, externally induced electric field gradients, and thermal spin-lattice interactions, for various relative orientations of the applied fields and the crystalline symmetry axes. The theoretical predictions were tested for the three nuclides ${\mathrm{Ga}}^{69}$, ${\mathrm{Ga}}^{71}$, and ${\mathrm{As}}^{75}$ by using pulsed nuclear magnetic resonance techniques to sample the equilibrium magnetization in a GaAs crystal at 77°K under the influence of a uniform, externally applied, radio-frequency, electric field. A description of the experimental apparatus is given. The dependence of the quadrupolar saturation on both the electric field amplitude and the crystal orientation was measured. The angular dependence of the saturation was found to be in reasonable agreement with the theory.