Spin-phonon coupling of Al2O3:V3+ by quantitative spectroscopy with phonons
Superconducting tunnel junctions were used as tunable monochromatic phonon sources by selecting a narrow band of bremsstrahlung phonons by modulation. For quantitative spectroscopy, the line shape of the modulated band was calculated. Using this, the experimental results on Al2O3: V3+ were analyzed in terms of the spinphonon Hamiltonian including rotational coupling. In contrast with the theory, the coupling with theL mode along the trigonal axis was not forbidden and, furthermore, exhibited an unexplained narrowing. The analysis of the other modes yieldedG44=+0.4 cm−1 andG41=− 8.1 cm−1. The observation of “resonance fluorescence” is also reported.