Calorimetric investigation on the paramagnetic–antiferromagnetic phase transition in CoO

Abstract The paramagnetic–antiferromagnetic phase transition of a single crystal of CoO, whose first- or second-order character is controversial, has been studied using a high sensitive calorimetric technique. Although both specific heat and differential thermal analysis (DTA) trace obtained at very low temperature rate (0.1 K h −1 ) show strong anomalies at the Neel temperature T N , the DTA trace and that calculated from the specific heat anomaly coincides indicating a continuous phase transition. In agreement with the theoretical predictions, the specific heat follows the 3D Ising model in a temperature range of 3 K below T N . Fisher relation for antiferromagnets is also obeyed in the same temperature range.