Magnetization and EPR studies of the single molecule magnet Ni4 with integrated sensors

Integrated magnetic sensors that allow simultaneous EPR and magnetization measurements have been developed to study single molecule magnets. A high frequency microstrip resonator has been integrated with a micro-Hall effect magnetometer. EPR spectroscopy is used to determine the energy splitting between the low lying spin states of a Ni4 single crystal, with an S=4 ground state, as a function of applied fields, both longitudinal and transverse to the easy axis at 0.4 K. Concurrent magnetization measurements show changes in spin population associated with microwave absorption. Such studies enable determination of the energy relaxation time of the spin system.