Thermodynamics of the two-dimensional Heisenberg classical honeycomb lattice

In this article we adapt a previous work concerning the two-dimensional (2D) Heisenberg classical square lattice [Physica B 245, 263 (1998)] to the case of a honeycomb lattice. Closed-form expressions of the main thermodynamic functions of interest are derived in the zero-field limit. Notably, near absolute zero (i.e., the critical temperature), we derive the values of the critical exponents alpha = 0, eta = -1, gamma = 3, and nu = 1, as for the square lattice, thus proving their universal character. A very simple model allows one to give a good description of the low-temperature behaviors of the product chi T. For 2D-compensated antiferromagnet, we derive simple relations between the characteristics of the maximum of the susceptibility curve T(chi(max)) and chi(max) and the involved exchange energies. Therefore, owing to the knowledge of T(chi(max)) and chi(max), one can directly obtain the respective values of these energies. Finally, we show that the theoretical model allows one to fit correctly experimental susceptibility data of the recently synthetized compound Mn-2(bpm)(ox)(2). 6H(2)O characterized by a 2D classical honeycomb lattice (where "bpm" and "ox" are the abbreviations for the ligands bipyrimidine and oxalate, respectively). [S0163-1829(98)04434-8].