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An EPR spin probe method for measuring magnetic field at the surface of single molecule magnets Fe8 and Mn12

Investigations of magnetic molecular clusters as microscopic devices at nanoscale range are currently in focus in magnetic recording and sensing technologies. The large magnetic molecules, which are combined to form crystal, behave like assembly of identical magnetic ions in identical environment and represent a new and attractive material for the potential applications [1, 2]. A spin probe method for measuring surface magnetic field for samples of the Single molecule magnet, SMM, Fe8[(tacn)6 O2(OH12)]Br89H2O (Fe8) and Mn12O12(CH3COO)16 (Mn12) will be discussed. The method uses as probe the EPR spectra of adsorbed diphenyl picrylhydrazil (DPPH). For both Fe8:DPPH it is shown that DPPH probe is sensitive to detect magnetic fluctuations in the superparamagnetic phase of SMM. The broadening of linewidth as well as shift of the position of Zeeman resonant field, H0 of the probe is detected for the superparamgnetic phase of SMM. Different amount of the shifts due to spontaneous magnetization, containing opposite sign along the easy axis and along hard crystal axis are detected. The obtained data are partly scaled (increasing shift with decreasing temperature) with SQUID data showing ability of the probe to track a change of the effective magnetic moments in the SMM crystal.

Relaxation; Nanomagnet; Behavior; Complex

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