Electron-nuclear double resonance of Ga in Mn-doped GaP

The hyperfine interactions of the first shell of Ga neighbors around ${\mathrm{Mn}}^{2+}$ on a Ga site in GaP are determined at 4.2 K by means of electron-nuclear double resonance (ENDOR) techniques. The spectrum could be described by use of the ENDOR spin Hamiltonian $\mathcal{H}=\overrightarrow{\mathrm{I}}·\overleftrightarrow{\mathrm{A}}·\overrightarrow{\mathrm{S}}+Q^{\prime }[I_{x_q}^2-\frac{1}{3}I(I+1\mathrm{})+\frac{1}{3}\eta (I_{y_q}^2-I_{z_q}^2\left)\right]-g_N{\beta }_N\overrightarrow{\mathrm{H}}·\overrightarrow{\mathrm{I}}$. The parameters of ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ga}$ are: $\frac{A_{x_h{x}_h}}{h}=+16.665\mathrm{}\pm 0.004$ MHz, $\frac{A_{y_h{y}_h}}{h}=+14.186\mathrm{}\pm 0.010$ MHz, $\frac{A_{z_h{z}_h}}{h}=+13.848\mathrm{}\pm 0.008$ MHz, $\frac{Q^{\prime }}{h}=-1.493\mathrm{}\pm 0.005$ MHz. $\eta =0.20\mathrm{}\pm 0.02$, and $\frac{g_N{\beta }_N}{h}=+1.298\mathrm{}\pm 0.003$ kHz/G. The $x_h$, $y_h$, and $z_h$ axes are the principal axes of $\overleftrightarrow{\mathrm{A}}$. The $z_h$ and $z_q$ axes coincide, and are along [$\overline{1}10$] for a Mn-Ga pair with axis along [110]. The angles between the pair axis and the $x_h$ and $x_q$ axes are 32.2±0.2° and 42.6±0.3°. respectively. The results for ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ga}$ are found to scale with those for ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ga}$ according to the ratios of the nuclear spins and the quadrupole moments. An attempt is made to interpret the data in terms of electron transfer and point-charge contributions.