Magnetic phase diagram of the organic antiferromagnet F4BImNN

Abstract

We present a combination of heat capacity and ac susceptibility measurements as a function of temperature and field, of a single crystal of the radical 2-(4,5,6,7-tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl. Our results confirm a zero-field Néel temperature at TN(0)=0.73K and allow the determination of the critical field parameters Hc(||)=170Oe and Hc(⊥)=306Oe. Assuming the previously determined 1-D intrachain ferromagnetic exchange interaction of Jintra/k=+22K between radicals, the interchain antiferromagnetic interaction is calculated as zJinter/k∼−0.03K.