Weak universal critical behaviour of the mixed spin‐(1/2, S ) Ising model on the Union Jack (centered square) lattice: integer versus half‐odd‐integer spin‐S case
Jozef Strečka, Lucia Čanová, J. Dely
Abstract The mixed spin‐(1/2, S ) Ising model on the Union Jack (centered square) lattice is investigated by establishing the mapping relationship with its corresponding eight‐vertex model. An interplay between the nearest‐neighbour interaction, the competing next‐nearest‐neighbour interaction and the single‐ion anisotropy gives rise to a rather complex critical behaviour displayed in the reentrant phase transitions, the weak universal critical behaviour, as well as, a presence of first‐ and second‐order phase transitions. The most interesting finding to emerge from the present study relates to a variation of the weak‐universal critical exponents along the line of bicritical points, which is being twice as large for the mixed spin‐(1/2, S ) systems with the integer spin‐S atoms as for the ones with the half‐odd‐integer spin‐S atoms. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
arXiv:cond-mat/0607473•physica status solidi (b)•May 9, 2006•11 citations