The measurement by scattering of the chiral order-parameter of spins in a crystal

TL;DR

This paper discusses how to measure the chiral order-parameter of spins in a crystal using total scattering techniques, clarifying misconceptions and proposing appropriate measurement methods.

Contribution

It clarifies that Bragg reflection measurements cannot determine spin chirality and advocates for total scattering methods to accurately measure the chiral order-parameter.

Findings

Bragg reflections do not reveal spin chirality.

Total scattering techniques can measure instantaneous spin correlations.

The paper corrects misconceptions in existing literature.

Abstract

A chiral-order parameter of spins in a crystal can not be inferred from measurements of Bragg reflections, although there are several claims in published literature to the contrary. Appropriate techniques use total scattering, of x-rays or neutrons, that yield the instantaneous value of a spin correlation related to an established measure of spin chirality.