High-frequency EPR spectroscopy of paramagnetic manganese centers in GaAs:Mn crystals

High-frequency electron paramagnetic resonance (EPR) is used to study the unique properties of manganese centers in a GaAs:Mn crystal in strong magnetic fields at low temperatures. At frequencies of 94 and 130 GHz, EPR transitions were recorded in the Mn$_{\mathrm{Ga}}^{2+}$-SH complex, which is a manganese ion with spin $S=5/2$, which replaces gallium (Mn$_{\mathrm{Ga}}^{2+}$) and is an ionized acceptor $(A^-)$ associated via an isotropic antiferromagnetic exchange interaction with a shallow hole (SH) with angular momentum $J=3/2$. A complex system of energy levels of this complex in a magnetic field and the possibility of accurately determining exchange interactions from EPR spectra are analyzed. Another complex was investigated, in which an ionized acceptor Mn$_{\mathrm{Ga}}^{2+}$ interacts with a localized hole center in the form of a diamagnetic ion O$_2$-replacing As. This complex, Mn$_{\mathrm{Ga}}^{2+}$-O$_{\mathrm{As}}^{2-}$, is characterized by axial symmetry along the $\langle111\rangle$ axis of the cubic GaAs crystal and an anisotropic EPR spectrum. Due to the high Boltzmann factor, in our studies, the order of the fine structure spin levels of this complex was determined. The effect of the Boltzmann populations of the energy levels on the high-frequency EPR spectra was also demonstrated for the Mn$_{\mathrm{Ga}}^{2+}$-SH complex.