Eur. Phys. J. B 37, 169-175 (2004)
https://doi.org/10.1140/epjb/e2004-00043-y

Thermodynamic properties of an alternating-spin (1/2,1) two-leg ladder

¹ Laboratory of Condensed Matter Spectroscopy and Opto-Electronic Physics, Department of Physics, Shanghai Jiao Tong University, 1954 Hua Shan Road, Shanghai 200030, P.R. China
² Department of Physics, Suzhou University, Suzhou, 215006, P.R. China

Corresponding author: ^a rom@wx88.net

Received: 2 April 2003
Revised: 24 October 2003
Published online: 15 March 2004

Abstract

With the aid of the Schwinger-boson mean-field method, we study the low-lying excitations and thermodynamic properties of a ferrimagnetic Heisenberg two-leg ladder (i.e., a ferrimagnetic double-chain with an antiferromagnetic interaction). The interaction between the two chains plays an important role in producing a low-lying excitation energy gap, affecting the low-lying excited spectrum, and increasing the disorder of the ferrimagnetic double-chain. The excitation spectrum, energy gap, and spin reduction in the ground state are calculated. Thermodynamic quantities such as the short-range spin correlation and short-range order are also obtained at low temperatures. In this gapful system, we observed the exponential behaviors in both the specific heat (C_V) and the product of magnetic susceptibility and temperature () at low temperatures. The exponential behavior of the  versus temperature agrees qualitatively with the experimental results in at low temperatures.