Experimental data obtained by electron paramagnetic resonance on silicon doped with aluminum and iron are presented. After quenching the sample and a short stay at room temperature, two spectra, labeled Si-NL27 and Si-NL28, were observed. It is concluded that the spectra originate from two Fe-A1 pairs with different symmetry. The spectra can be described with an effective spin $J=\frac{1}{2}$ and $g$ factors significantly deviating from 2. A theoretical investigation of the $g$-value tensors of iron-acceptor pairs allows an interpretation of the $g$ factors in terms of crystal-field splitting and spin-orbit coupling.

• Received 6 June 1984

DOI:https://doi.org/10.1103/PhysRevB.30.4564