Magnetic field versus temperature phase diagram of a quasi-one-dimensional S=1 Heisenberg antiferromagnet

From a heat capacity (C-p) measurement on a single crystal sample of the S = 1 quasi-one-dimensional(Q1D) Heisenbeg antiferromagnet (HAF) Ni(C5H14N2)(2)N-3(PF6) in applied magnetic fields, we found an anomaly which is indicative of a magnetic long-range ordering. We were able to follow how the position of the anomaly in C-p changes with temperature (T) and magnetic field (H). An experimental H-T phase diagram of an S = 1 Q1D HAF is obtained and compared with that of the corresponding classical system. [S0031-9007(98)07105-1].