Ferrimagnetic mixed-spin ladders in weak and strong coupling limits

TL;DR

This paper investigates ferrimagnetic mixed-spin ladders with ferromagnetic legs, analyzing their spectra and correlations in weak and strong coupling limits using various theoretical methods, revealing how antiferromagnetic rung coupling affects long-range order.

Contribution

It introduces and compares two ferrimagnetic ladder models, applying multiple theoretical approaches to understand their spectral and correlation properties across coupling regimes.

Findings

Antiferromagnetic rung coupling destroys long-range order.

Weak coupling regime analyzed with spin-wave theory and bosonization.

Strong coupling limits show transition to antiferromagnetic chain behavior.

Abstract

We study two similar spin ladder systems with the ferromagnetic leg coupling. First model includes two sorts of spins, s= 1/2 and s= 1, and the second model comprises only s=1/2 legs coupled by a "triangular" rung exchange. The antiferromagnetic (AF) rung coupling destroys the long-range order and eventually makes the systems equivalent to the AF s=1/2 Heisenberg chain. We investigate the situation by different methods in weak and strong rung coupling limits. Particularly we compare the spin-wave theory and the bosonization method in the weak coupling regime of the second model. We analyze the spectra and correlations, and discuss the order parameter of these ladder systems.