Two-dimensional Heisenberg antiferromagnet in a transverse field

TL;DR

This paper studies how a transverse magnetic field affects a 2D anisotropic antiferromagnet, revealing that the magnetization perpendicular to the field initially increases due to fluctuation suppression, with implications for magnetic reorientation.

Contribution

It introduces a many-body Green's function approach to analyze magnetic reorientation in a 2D antiferromagnet under a transverse field, highlighting a novel fluctuation suppression mechanism.

Findings

Magnetization perpendicular to the field initially increases with field strength.

Suppression of quantum and thermal fluctuations causes this increase.

Magnetic reorientation occurs above the Néel temperature.

Abstract

We investigate the magnetic reorientation in a two-dimensional anisotropic antiferromagnet due to a transverse magnetic field. Using a many-body Green's function approach, we show that the magnetization component perpendicular to the applied field (and along the easy-axis of the antiferromagnet) initially increases with increasing field strength. We show that this unexpected result arises from the suppression of quantum and thermal fluctuations in the antiferromagnet. Above the N\'eel temperature, this effect leads to a reappearance of a magnetic moment along the easy-axis.