Field-induced magnetic charge in a cubic Laves compound UAl2

TL;DR

This study reveals field-induced magnetic charges in UAl2 through polarized neutron diffraction, identifying weak forbidden Bragg spots as Dirac multipoles, advancing understanding of magnetic multipole phenomena in cubic compounds.

Contribution

It introduces the concept of field-induced magnetic charge via Dirac multipoles in UAl2, supported by diffraction pattern analysis with a magnetic space-group model.

Findings

Weak forbidden Bragg spots are explained as Dirac multipoles.

The diffraction pattern matches calculations including Dirac dipoles.

Magnetic charge phenomena are demonstrated in a cubic Laves compound.

Abstract

Magnetic diffraction of polarized neutrons by the cubic Laves compound UAl2 in a magnetic field has unveiled weak Bragg spots that are nominally forbidden. On the one hand, they can be viewed as magnetic analogues of the basis-forbidden (2, 2, 2) reflection in diamond-type structures that has been painstakingly and frequently investigated over almost a century. Alternatively, the pattern of weak intensities can be assigned to Dirac multipoles imbedded in field-induced magnetic charge. To this end, a published diffraction pattern is successfully confronted with intensities calculated from the appropriate magnetic space-group that includes Dirac dipoles (anapoles) to describe the basis-forbidden magnetic reflections, and conventional (axial) dipole and octupole multipoles to describe basis-allowed magnetic reflections.