EPR characterization of diamagnetic and magnetic organic soft materials using nitroxide spin probe techniques

This review article summarizes the recent advances in the EPR studies of the molecular orientation and magnetic properties in the various rod-like liquid crystalline (LC) phases of the second-generation of organic nitroxide radical materials in the bulk state or in a surface-stabilized LC cell, compared with the conventional EPR studies using classical organic nitroxide spin probes. Noteworthy is the first observation and characterization of a sort of spin glass-like ferromagnetic interactions (J > 0) induced by weak magnetic fields in the various LC phases of the second-generation of organic nitroxide radical materials. This unique magnetic property has been referred to as positive “magneto-LC effects”. The utility of such novel LC nitroxide radical materials as the EPR spin probes is also presented.