Muonium states in germanium

An anomalous muonium state similar to that in silicon has been found in germanium. This state can be described an anisotropic hyperfine interaction with the parameters $\frac{A_{\perp }}{h}=130.7\mathrm{}\pm 1$ MHz and $\frac{A_{\parallel }}{h}=26.8\mathrm{}\pm 1$ MHz. In contrast to Si this anomalous muonium state in Ge was not observed at low external fields. In addition, a detailed investigation of normal muonium in Ge was carried out. For undoped Ge the hyperfine constant is found to be temperature independent in the range between 6 and 81 K with an average value of $\frac{A\left(\mathrm{Ge}\right)}{h}=2361\mathrm{}\pm 3$ MHz or $\frac{A\left(\mathrm{Ge}\right)}{A\left(\mathrm{vac}\right)}=0.5290\mathrm{}\pm 0.0007$. The present value is considerably lower than that published by Gurevich et al. The relaxation rate of normal muonium in the Ge sample investigated increases sharply above about 50 K with an activation energy of 14 meV. A correlation with the thermal activation of impurity charge carriers is suggested.