Preparation of a novel thin film utilizing a magnetic field: Alignment of organic microcrystals as revealed by atomic force microscopy

Novel organic thin solid films were prepared by casting a tetrahydrofuran solution of nOCB (4-alkoxy-4'cyanobiphenyls) where n denotes the number of methylenes in the substituent) in the presence of a horizontal magnetic field. Atomic force microscopy of the 8OCB film revealed that needle-type crystals with micrometer dimensions were well oriented with a perpendicular alignment to the magnetic field. This thin film reflected rays of light in a similar manner to a diffraction grating. In the case of 12OCB which forms plate-type crystals, no such crystal orientation was observed, although its molecular magnetic susceptibility is almost the same as that of 8OCB. We consider that crystal form anisotropy is necessary for the observation of the orientational pattern.