Affiliation: | (1) Laboratory of Condensed Matter Spectroscopy and Opto-Electronic Physics, Department of Physics, Shanghai Jiao Tong University, 1954 Hua Shan Road, 200030 Shanghai, P.R. China;(2) Department of Physics, Suzhou University, 215006 Suzhou, P.R. China |
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 (CV) 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.Received: 24 October 2003, Published online: 15 March 2004PACS: 75.10.Jm Quantized spin models - 75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.) - 75.50.Ee Antiferromagnetics - 75.50.Gg Ferrimagnetics |