Organic magnetism in nitronyl nitroxides studied by mu SR

Ferromagnetism has been observed in a family of organic molecular crystals based on the nitronyl nitroxide radical. We present the results of mu SR experiments on a number of nitronyl nitroxide compounds. The zero-field spin precession of muons implanted in diamagnetic states can be used to follow the magnetic order parameter as a function of temperature. Five of the materials studied show magnetic transitions, although the transition temperature and the nature of the magnetic ground state in each case are quite different. mu SR can be used to study these ground states and thus help to relate the observed magnetic properties to the crystal structure of each material.