INFLUENCE OF SPIN FLUCTUATION ON THERMODYNAMIC PROPERTIES OF QUANTUM SPIN CHAIN WITH ISOTROPIC HEISENBERG MODEL

Abstract

Dependence of the thermodynamic properties of the quantum spin chain on temperature and external magnetic field is investigated using the functional integral method with short range exchange interaction in isotropic Heisenberg model. The results in mean field approximation (MFA) and spin fluctuation approximation (SFA) are showed and compared with ones of other authors. Besides, the spin fluctuation breaks magnetic order in low dimensional spin systems with the short range exchange interaction in the isotropic Heisenberg model without the external magnetic field.