Instability of a ferrimagnetic state of a frustrated S=1/2 Heisenberg antiferromagnet in two dimensions

TL;DR

This study investigates the stability of ferrimagnetic order in a two-dimensional frustrated S=1/2 Heisenberg antiferromagnet, revealing its discontinuous disappearance with increasing frustration and magnetic field.

Contribution

It provides numerical evidence of the instability and disappearance of ferrimagnetism in a frustrated 2D quantum antiferromagnet, highlighting the effects of frustration and magnetic fields.

Findings

Ferrimagnetic ground state exists at low frustration.

Spontaneous magnetization vanishes discontinuously at a critical frustration.

Ferrimagnetism disappears even under magnetic field with further frustration.

Abstract

To clarify the instability of the ferrimagnetism which is the fundamental magnetism of ferrite, numerical-diagonalization study is carried out for the two-dimensional S=1/2 Heisenberg antiferromagnet with frustration. We find that the ferrimagnetic ground state has the spontaneous magnetization in small frustration; due to a frustrating interaction above a specific strength, the spontaneous magnetization discontinuously vanishes so that the ferrimagnetic state appears only under some magnetic fields. We also find that, when the interaction is increased further, the ferrimagnetism disappears even under magnetic field.