Combination of Ferromagnetic and Antiferromagnetic Features in Heisenberg Ferrimagnets

TL;DR

This paper studies the thermodynamic behavior of Heisenberg ferrimagnetic chains, revealing unique ferromagnetic and antiferromagnetic features through advanced numerical and analytical methods.

Contribution

It introduces a new density-matrix renormalization-group technique and develops a modified spin-wave theory to analyze ferrimagnetic chains.

Findings

Low-temperature specific heat behaves as T^{1/2}

Magnetic susceptibility times temperature behaves as T^{-1}

Intermediate temperatures show a Schottky-like peak and a minimum

Abstract

We investigate the thermodynamic properties of Heisenberg ferrimagnetic mixed-spin chains both numerically and analytically with particular emphasis on the combination of ferromagnetic and antiferromagnetic features. Employing a new density-matrix renormalization-group technique as well as a quantum Monte Carlo method, we reveal the overall thermal behavior: At very low temperatures, the specific heat and the magnetic susceptibility times temperature behave like $T^{1/2}$ and $T^{-1}$, respectively, whereas at intermediate temperatures, they exhibit a Schottky-like peak and a minimum, respectively. Developing the modified spin-wave theory, we complement the numerical findings and give a precise estimate of the low-temperature behavior.