Magnetic Langmuir-Blodgett films with metal-oxalato complexes

Langmuir-Blodgett (LB) films containing various oxalato complexes were prepared using the so-called semiamphiphilic approach where inorganic ions are adsorbed along a charged monolayer. In a first series of experiments, lamellar materials based on monometallic oxalato complexes (with Fe-III or Cr-III) have been characterized by X-ray diffraction, XPS, FTIR, ESR, and SQUID measurements. The metal complexes are organized either in monolayers or in bilayers within the LB films, depending on the charge density of the organic layer. Within each inorganic layer, the complexes present a particular orientation or distortion. Finally, the magnetic behavior of such LB films is simply described by the Curie law. In a second series of experiments, synthesized heterobimetallic complexes based on a M-1(III)-M-2(II)-M-1(III) trimer have been organized thanks to the LB technique. Magnetization measurements made on these multilayers show a deviation from the Curie law and from that observed in the powder. They emphasize the interest to control perfectly the molecular organization in order to build up specific extended magnetic systems.