EPR anisotropy induced by a magnetic field in the smectic A phase of a mesogenic Cu(II) complex derived from a Schiff's base

The Q-band electron paramagnetic resonance (EPR) spectrum of the frozen smectic phase of the mesogenic compound bisN -(4'-n-pentoxyphenyl)-4-n-decyloxysalicylaldiminate] copper(II) is studied. An anisotropic EPR spectrum is observed if freezing from the SmA phase is done in the presence of a magnetic field; the sample tends to orient with the director perpendicular to the magnetic field. The relative intensities of the EPR signal of this exchange coupled system are discussed in relation to the orientational distribution of the molecules. The results appear to be compatible with a biaxial magnetic susceptibility in the SmA phase. This suggests that an ordering of the short axes of the molecules in the plane perpendicular to the director in the SmA mesophase may take place.