Magnetic Compton profile in non-magnetic ferroelectrics

TL;DR

This paper demonstrates that non-magnetic ferroelectric materials can exhibit a magnetic Compton profile that is electrically controllable, revealing hidden magnetoelectric multipoles in momentum space.

Contribution

It introduces the concept of magnetic Compton profiles in non-magnetic ferroelectrics and links them to $k$-space magnetoelectric multipoles, enabling electrical control and measurement.

Findings

Non-magnetic ferroelectrics can have a non-zero magnetic Compton profile.

The magnetic Compton profile is antisymmetric and reversible with electric fields.

PbTiO$_3$ shows a spin asymmetry linked to a $k$-space magnetoelectric toroidal moment.

Abstract

Magnetic Compton scattering is an established tool for probing magnetism in ferromagnetic or ferrimagnetic materials with a net spin polarization. Here we show that, counterintuitively, {\it non-magnetic} systems can also have a non-zero magnetic Compton profile, provided that space-inversion symmetry is broken. The magnetic Compton profile is antisymmetric in momentum and, if the inversion symmetry is broken by an electric-field switchable ferroelectric distortion, can be reversed using an electric field. We show that the underlying physics of the magnetic Compton profile and its electrical control are conveniently described in terms of $k$-space magnetoelectric multipoles, which are reciprocal to the real-space charge dipoles associated with the broken inversion symmetry. Using the prototypical ferroelectric lead titanate, PbTiO$_3$, as an example, we show that the ferroelectric polarization introduces a spin asymmetry in momentum space that corresponds to a pure $k$-space magnetoelectric toroidal moment. This in turn manifests in an antisymmetric magnetic Compton profile which can be reversed using an electric field. Our work suggests an experimental route to directly measuring and tuning hidden $k$-space magnetoelectric multipoles via their magnetic Compton profile.