Spin Dynamics of a Canted Antiferromagnet in a Magnetic Field

TL;DR

This paper investigates the unique spin-wave dynamics in canted antiferromagnets under magnetic fields, revealing field-dependent signatures that distinguish them from phase-separated magnetic mixtures.

Contribution

It demonstrates the field-dependent behavior of spin-wave stiffness and gap energy in canted antiferromagnets, providing a method to differentiate them from mixed magnetic phases.

Findings

Spin-wave stiffness depends on magnetic field and wavevector limits.

Field dependence of spin-wave properties distinguishes canted antiferromagnets.

Unique signatures appear when anisotropy gap is negligible.

Abstract

The spin dynamics of a canted antiferromagnet with a quadratic spin-wave dispersion near $\vq =0$ is shown to possess a unique signature. When the anisotropy gap is negligible, the spin-wave stiffness $\dsw (\vq, B) = (\omega_{\vq}-B)/q^2$ depends on whether the limit of zero field or zero wavevector is taken first. Consequently, $\dsw $ is a strong function of magnetic field at a fixed wavevector. Even in the presence of a sizeable anisotropy gap, the field dependence of both $\dsw $ and the gap energy distinguishes a canted antiferromagnet from a phase-separated mixture containing both ferromagnetic and antiferromagnetic regions.