Specific heat and magnetic entropy of Na1−xV2O5

Abstract The specific heat of Na 1− x V 2 O 5 ( x =0, 0.01, 0.02, 0.03, 0.04) single crystalline samples was investigated in a temperature range 6–300 K. With deviation from stoichiometry the phase transition temperature and the energy gap in the magnetic excitation spectrum rapidly decrease. The specific heat anomaly becomes smaller and is not observed for x >0.03. The magnetic entropy released at the critical temperature in NaV 2 O 5 ∼7.7 J/mol K and decreases with x .