Nonconventional magnetic order in frustrated diamond lattice antiferromagnet CoAl2O4 studied by neutron diffraction and classical Monte-Carlo simulation

TL;DR

This study investigates the complex magnetic behavior of CoAl2O4, a frustrated diamond lattice antiferromagnet, using neutron diffraction and Monte Carlo simulations to understand the effects of interactions, magnetic fields, and microstructure.

Contribution

The paper introduces a combined experimental and simulation approach to analyze magnetic order in CoAl2O4, highlighting the role of microstructure in its unconventional magnetic properties.

Findings

Models explain broadening of magnetic Bragg peaks partly.

Anisotropic response to magnetic fields observed.

Microstructure, especially <111>-twin boundaries, may influence magnetic order.

Abstract

CoAl2O4 spinel with magnetic Co2+ ions on the diamond A-lattice is known to be magnetically frustrated. We compare neutron single crystal diffraction patterns measured in zero and applied magnetic fields with the ones obtained from classical Monte-Carlo models. In simulations we test the influence of various parameters on diffraction patterns: the ratio of nearest-, J1, and next-nearest, J2, neighbor interactions, magnetic field applied along the principal crystallographic directions, and random disorder on the A(Co2+)- and B(Al3+)- sites. We conclude that the models considered so far explain the broadening of magnetic Bragg peaks in zero magnetic field and their anisotropic response to applied magnetic field only partly. As bulk properties of our single crystal are isotropic, we suggest that its microstructure, specifically <111>-twin boundaries, could be a reason of the nonconventional magnetic order in CoAl2O4.