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arXiv:1006.0794 · Physical Review B

Magnetism and thermodynamics of spin- (12,1) decorated Heisenberg chain with spin-1 pendants

Shou-Shu Gong, Wei Li, Yang Zhao, Gang Su

Published Jun 21, 2010• 22 citations
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Abstract

The magnetic and thermodynamic properties of a ferrimagnetic decorated spin-$(\frac{1}{2},1)$ 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) ${J}_{1}<0$ and ${J}_{2}>0$, where ${J}_{1}$ and ${J}_{2}$ 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 $m=\frac{3}{2}$ ($m$ is the magnetization per unit cell) plateau is observed for case (A), while two plateaux at $m=\frac{1}{2}$ and $\frac{3}{2}$ 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 $\ensuremath{\chi}T$ and specific heat exhibit distinct exotic features with varying the couplings and temperature for different cases. $\ensuremath{\chi}T$ is found to converge as $T\ensuremath{\rightarrow}0$, which is different from the divergent behavior in the spin-$(\frac{1}{2},1)$ mixed-spin chain without pendants. The observed thermodynamic behaviors are also discussed with the help of their low-lying excitations.

DOI
10.1103/physrevb.81.214431

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