X-Ray Detected Magnetic Hysteresis of Thermally Evaporated Terbium Double-Decker Oriented Films

Successful attempts to deposit SMMs in UHV conditions have been carried out with a tetranuclear iron(III) cluster [ 9 ] and lanthanide bis-phthalocyaninato (LnPc 2 ) complexes. [ 10 , 11 ] For the latter the seminal works of Ishikawa et al. [ 12 ] showed that slow dynamics of the magnetization in these mononuclear complexes is originated directly from their strong single ion anisotropy. Very recently a structural and magnetic characterization of a sub-monolayer deposit TbPc 2 based on synchrotronlight techniques has confi rmed that this magnetic anisotropy is retained on surface. [ 13 ] The absence of the observation of typical slow dynamics of the magnetization has been attributed to the long time-scale of the X-ray based experiments. We report here a synchrotron-based investigation on neutral TbPc 2 evaporated thick and thin fi lms evidencing that the thick fi lm of TbPc 2 is characterized by slow relaxation of the magnetization and opening of a butterfl y hysteresis cycle at temperatures as high as 15 K but not observed for the thin fi lm. These differences are accompanied with a drastic change in the orientation of the TbPc 2 molecules in the two fi lms