Determination of the quadrupole splitting in bulk $n$-GaAs by warm-up spectroscopy

We found bulk $n$-GaAs layers grown by liquid phase epitaxy to be irregularly stressed. Deformation created by this stress causes a small but detectable quadrupole splitting of Zeeman nuclear energy levels. In our work we detected a very weak quadrupole splitting for $^{69}$Ga and $^{75}$As isotopes in bulk $n$-GaAs and obtained the value of the sample deformation. To this end, we used a new method that we call warm-up spectroscopy of nuclear spins in weak external magnetic fields.