An Organic Ferromagnet with a Tc of 0.4 K. 4-(p-Phenylbenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-oxyl

The polycrystalline sample of the title radical has a positive Weiss constant of 0.63 K. The ac susceptibility measurements indicated a ferromagnetic phase transition at about 0.4 K. The magnetization measured at 80 mK (below Tc) showed a characteristic curve of a ferromagnet with a small hysteresis. The X-ray crystal structure analysis at room temperature revealed a two-dimensional network of the N–O sites (O···O distances are 5.96 and 6.09 Å) with an inter-sheet distance of 14.2 Å.