Abstract: Friedman

Prof. Jonathan Friedman – Amherst College

Title: “Relaxation and Tunneling in Single-Molecule Magnets”

A single-molecule magnet is – true to its name – a magnet composed of a single molecule. The magnetic moment of such a system shows hysteresis like a classical magnet, yet it can tunnel between different orientation states. Single-molecule magnets typically have a large spin (~10) whose dynamics can be described using a double-well potential where one well corresponds to the spin pointing up and the other to it pointing down. An external field tilts the potential and at certain values of the field, energy levels in opposite wells align, causing resonant tunneling and a concomitant increase in the magnetic reversal rate. The tunneling can be modulated by a remarkable interference effect brought about by the interference among multiple tunneling paths. Microwave radiation resonant with the transition between two spin-orientation levels can be used to enhance the relaxation process and allow the observation of tunneling phenomena on sub-microsecond time scales.