Abstract
The crystalline nitroxide biradical, 1,2,5,7-tetramethyl-2,6-diazaadamantane N,N′-dioxyl, shows ferromagnetic interactions in the solid: a positive Weiss-constant θ= 10 K, a large χT increase at low temperature (T < 20 K) and a magnetisation curve consistent with a total spin S= 6.