LANGMUIR-BLODGETT-FILMS OF KNOWN LAYERED SOLIDS - PREPARATION AND STRUCTURAL-PROPERTIES OF OCTADECYLPHOSPHONATE BILAYERS WITH DIVALENT METALS AND CHARACTERIZATION OF A MAGNETIC LANGMUIR-BLODGETT-FILM

Langmuir-Bodgett (LB) films of a series of divalent metal octadecylpho sphonates have been prepared and characterized. The films are each sho wn to be LB analogs of known solid-state metal phosphonates possessing 2-dimensional ionic-covalent metal phosphonate layers. The metal phos phonate layers crystallize during the LB deposition process. Films wer e characterized with XPS, X-ray diffraction, ellipsometry, attenuated total reflectance FTIR, and, in the case of the manganese film, SQUID magnetometry. Octadecylphosphonate films with Mn2+, Mg2+, and Cd2+ for m with the stoichiometry M(O3PC17H37). H2O and have metal phosphonate bonding consistent with the analogous M(O3PR). H2O layered solids. The Ca2+ film forms as Ca(HO3PC18H37)(2), which is also a known solid-sta te phase. Magnetic measurements reveal that the manganese octadecylpho sphonate film undergoes a magnetic ordering transition at 13.5 K resul ting in a ''weak ferromagnet''. The behavior is similar to that of the known layered solid-state manganese alkylphosphonates which are also ''weak ferromagnets''. The magnetic ordering is antiferromagnetic wher e incomplete cancellation of the magnetic sublattices, due to low site symmetry, results in a spontaneous magnetization. A spin-flop transit ion is observed at 2.5 T in magnetization vs applied field measurement s of the ordered state. The film also exhibits magnetic memory, with a small remnant magnetization and a coercive field of 20 mT at 2 K. The results demonstrate that magnetic ordering phenomena can be incorpora ted into LB films and that LB film methods can be used to prepare mono layer and multilayer films of known solid-state materials.