Strange magnetic multipoles and neutron diffraction by an iridate perovskite (Sr2IrO4)

TL;DR

This paper predicts the existence of novel magnetic multipoles in iridate perovskites, demonstrating their influence on neutron diffraction and expanding understanding beyond the traditional jeff=1/2 model.

Contribution

It introduces the concept of strange magnetic multipoles in iridate perovskites and shows their impact on neutron diffraction, extending the theoretical framework beyond the jeff=1/2 model.

Findings

Strange multipoles are parity-even, time-odd, even-rank tensors absent in previous models.

Strange multipoles contribute significantly to neutron diffraction intensities.

Triakontadipoles have a relatively small contribution compared to quadrupoles and hexadecapoles.

Abstract

A theoretical investigation of a plausible construct for electronic structure in iridate perovskites demonstrates the existence of magnetic multipoles hitherto not identified. The strange multipoles, which are parity-even, time-odd and even rank tensors, are absent from the so-called jeff = 1/2 model. We prove that the strange multipoles contribute to magnetic neutron diffraction, and we estimate their contribution to intensities of Bragg spots for Sr2IrO4. The construct encompasses the jeff = 1/2 model, and it is consistent with the known magnetic structure, ordered magnetic moment, and published resonant x-ray Bragg diffraction data. Over and above time-odd quadrupoles and hexadecapoles, whose contribution changes neutron Bragg intensities by an order of magnitude, according to our estimates, are relatively small triakontadipoles recently proposed as the primary magnetic order-parameter of Sr2IrO4.