Magnetic ordering in nitroxide multiradicals

Abstract

A ferromagnetic transition has been observed in single crystals of 1,3,5,7-tetramethyl-2,6-diazaadamantane-N,N'-dioxyl ("Dupeyredioxyl"). It is characterized by a divergence of the a.c. susceptibility and the onset of spontaneous magnetization at Tc = 1.48 K. No hysteresis was detected. The a.c. and d.c. susceptibility have a quite similar temperature dependence. In the molecule the two unpaired electrons are mainly located on each NO group. In the crystal, each NO group has three close neighbours (at ca. 4.5 Å): two on two different molecules and one in the same molecule, suggesting a 3D network of chains connected through intramolecular interactions.