Classical and quantum magnetisation reversal studied in single nanometer-sized particles and clusters using micro-SQUIDs

摘要

Recent progress in experiment on quantum tunnelling of the magnetic moment inmesoscopic systems will be reviewed. The emphasis will be made on measurementsof individual nanoparticles. These nanomagnets allow one to test the borderbetween classical and quantum behaviour. Using the micro-SQUID magnetometer,waiting time, switching field and telegraph noise measurements showunambiguously that the magnetisation reversal of small enough singlecrystalline nanoparticles is described by a model of thermal activation over asingle-energy barrier. Results on insulating BaFeO nanoparticles show strongdeviations from this model below 0.4 K which agree with the theory ofmacroscopic quantum tunnelling in the low dissipation regime.