MESOSCOPIC QUANTUM TUNNELING OF THE MAGNETIZATION

Magnetic relaxation plateaux observed at low temperature in complex systems, are generally attributed to Quantum Tunneling of the Magnetization (QTM). If the experiments are not performed down to low enough temperatures, alternative interpretations can be given in terms of powerlaw distributions resulting from either switching field distributions or/and coupling between switching blocks leading to self-organized criticality. Besides, the first low-temperature/time-dependent magnetization experiments, performed on single sub-micronic particles and on arrays nanoparticles in molecular crystals, are described.