Shou-Shu Gong, Wei Li, Yang Zhao, and Gang Su *
College of Physical Sciences, Graduate University of Chinese Academy of Sciences, P.O. Box 4588, Beijing 100049,
People’s Republic of China
(Received 15 March 2010; revised manuscript received 24 May 2010; published 21 June 2010)

Abstract:

      The magnetic and thermodynamic properties of a ferrimagnetic decorated spin-(1/2 ,1) Heisenberg chain with spin-1 pendant spins are investigated for three cases: (A) J ₁ ,J ₂ >0; (B) J ₁ >0 and J ₂ <0; and (C)J ₁ <0 andJ₂ >0, where J₁ and J₂ are the exchange couplings between spins in the chain and along the rung, respectively. The low-lying and magnetic properties are explored jointly by the real-space renormalization group, spin wave,and density-matrix renormalization-group methods, while the transfer-matrix renormalization-group method is invoked to study the thermodynamics. It is found that the magnon spectra consist of a gapless and two gapped branches. Two branches in case (C) have intersections. The coupling dependence of low-energy gaps are analyzed. In a magnetic field, a m=3/2 (m is the magnetization per unit cell) plateau is observed for case (A), while two plateaux at m=1/2 and 3/2 are observed for cases ?B? and ?C?. Between the two plateaux in cases (B) and (C), the sublattice magnetizations for the spins coupled by ferromagnetic interactions have decreasing regions with increasing the magnetic field. At finite temperature, the zero-field susceptibility temperature product χT and specific heat exhibit distinct exotic features with varying the couplings and temperature for different cases.  χT is found to converge as T→0, which is different from the divergent behavior in the spin-(1/2 ,1) mixed-spin chain without pendants. The observed thermodynamic behaviors are also discussed with the help of their low-lying excitations.