Low-temperature thermodynamics of one-dimensional alternating-spin Heisenberg ferromagnets

TL;DR

This paper studies the thermodynamic behavior of one-dimensional alternating-spin ferromagnetic chains using numerical and analytical methods, revealing unique thermal features and low-temperature properties relevant to bimetallic compounds.

Contribution

It combines quantum Monte Carlo simulations with a modified spin-wave theory to analyze thermodynamics of mixed-spin ferromagnets, highlighting their distinctive thermal and magnetic characteristics.

Findings

Double-peaked specific heat at intermediate temperatures for S ≥ 3s

Accurate low-temperature descriptions via modified spin-wave theory

Identified similarities and differences with ferrimagnets

Abstract

Motivated by a novel bimetallic chain compound in which alternating magnetic centers are ferromagnetically coupled, we investigate thermodynamic properties of one-dimensional spin-$(S,s)$ Heisenberg ferromagnets both numerically and analytically. On the one hand, quantum Monte Carlo calculations illuminate the overall thermal behavior. The specific heat may exhibit a double-peaked structure at intermediate temperatures for $S\agt 3s$ in general. On the other hand, a modified spin-wave theory precisely describes the low-temperature properties. Expanding the specific heat and the magnetic susceptibility, we reveal an analogy and a contrast between mixed-spin ferromagnets and ferrimagnets.