Thermodynamic properties of a tetramer   ferro-ferro-antiferro-antiferromagnetic Ising-Heisenberg bond alternating   chain as a model system for Cu(3-Clpy)$_2$(N$_3$)$_2$
  Thermodynamic properties of a tetramer ferro-ferro-antiferro-antiferromagnetic Ising-Heisenberg bond alternating chain are investigated by the use of an exact mapping transformation technique. Exact results for the magnetization, susceptibility and specific heat in the zero as well as nonzero magnetic field are presented and discussed in detail. The results obtained from the mapping are compared with the relevant experimental data of Cu(3-Clpy)$_2$(N$_3$)$_2$ (3-Clpy=3-Chloropyridine). 
Jozef Strecka, Michal Jascur, Masayuki Hagiwara, Kazuhiko Minami,   Yasuo Narumi and Koichi Kindo