Thermodynamic properties of the XY ferrimagnetic spin-(1/2,1) chain with both longitudinal and transverse single-ion anisotropies

We investigate the finite temperature properties of the mixed spin-1/2 and spin-1 ferrimagnetic chain with both longitudinal single-ion anisotropy D z and transverse single-ion anisotropy D x . The spin excitation spectrum as well as the thermodynamic quantities are explored by means of the Villian transformation theory. We find two branches of the low-lying energy spectrum are strongly dependent on the model Hamiltonian parameters J 1 , J 2 , D z , D x . Our results agree well with the exact method results for the mixed spin-1/2 and spin-1 Ising chain. The thermodynamic quantities of XY ferrimagnetic spin- ( 1 / 2 , 1 ) chain varying with D z and D x , such as free energy, internal energy, entropy, specific heat and magnetization are explicitly discussed, respectively. The result shows that the magnetization plateaux exists in XY ferrimagnetic spin chain without anisotropy, which indicates a phase transition may occur in XY ferrimagnetic spin chain.