Crossover between Thermally Assisted and Pure Quantum Tunneling in Molecular Magnet Mn12-Acetate

The crossover between thermally assisted and pure quantum tunneling has been studied in single crystals of high spin \(S = 10\) uniaxial molecular magnet Mn₁₂ using micro-Hall-effect magnetometry. Magnetic hysteresis and relaxation experiments have been used to investigate the energy levels that determine the magnetization reversal as a function of magnetic field and temperature. These experiments demonstrate that the crossover occurs in a narrow \(~0.1 K\) or broad \(~1 K\) temperature interval depending on the magnitude of the field transverse to the anisotropy axis.