Neutral Mn acceptor in bulk GaN in high magnetic fields

We present magneto-optical studies of intra-center absorption band related to neutral Mn acceptor in GaN bulk crystals. The band is built of a zero-phonon line at 1.41660.3em0exeV followed by GaN phonon spectrum. Magneto-optical experiments performed in magnetic fields up to 220.3em0exT in both Faraday and Voigt configurations revealed very small influence of magnetic field on the spectrum. In particular no splitting of the zero-phonon line was observed. The only characteristic feature recorded in high magnetic fields was a step-like behavior of the spectral position of zero-phonon line measured in Faraday configuration. The step appeared at the magnetic field of about 70.3em0exT, with a shift in energy of about 1.30.3em0exmeV. We interpret the behavior of the zero-phonon line in magnetic field based on crystal-field model for Mn³⁺(d⁴) ion in trigonal crystal field, undergoing Jahn-Teller distortion and spin-orbit coupling. Applied model explains reasonably experimental results, supporting strongly localized character of Mn neutral acceptor in GaN.