# Partial Ferrimagnetism in S=1/2 Heisenberg Ladders with a Ferromagnetic Leg, an Antiferromagnetic Leg, and Antiferromagnetic Rungs

## TL;DR

This paper investigates the ground-state and finite-temperature properties of a specific S=1/2 Heisenberg ladder model, revealing a wide partial ferrimagnetic phase characterized by spontaneous magnetization and incommensurate correlations, supported by numerical and analytical methods.

## Contribution

It introduces the existence of a broad partial ferrimagnetic phase in a mixed-leg Heisenberg ladder, combining numerical, analytical, and perturbative approaches to characterize its properties.

## Key findings

- Partial ferrimagnetic phase extends over a wide parameter range.
- The phase is a spontaneously magnetized Tomonaga–Luttinger liquid.
- Finite-temperature susceptibility diverges as T^{-2}.

## Abstract

Ground-state and finite-temperature properties of $S=1/2$ Heisenberg ladders with a ferromagnetic leg, an antiferromagnetic leg, and antiferromagnetic rungs are studied. It is shown that a partial ferrimagnetic phase extends over a wide parameter range in the ground state. The numerical results are supported by an analytical calculation based on a mapping onto the nonlinear $\sigma$ model and a perturbation calculation from the strong-rung limit. It is shown that the partial ferrimagnetic state is a spontaneously magnetized Tomonaga--Luttinger liquid with incommensurate magnetic correlation, which is confirmed by a DMRG calculation. The finite-temperature magnetic susceptibility is calculated using the thermal pure quantum state method. It is suggested that the susceptibility diverges as $T^{-2}$ in the ferrimagnetic phases as in the case of ferromagnetic Heisenberg chains.