Coexisting order and disorder hidden in a quasi-two-dimensional frustrated magnet

TL;DR

This study explores the complex magnetic states in a quasi-two-dimensional pyrochlore lattice, revealing a systematic approach to understanding coexisting order and disorder, and matching experimental data with theoretical models.

Contribution

It introduces a novel mapping of the frustrated magnetic problem onto a model with two degrees of freedom, aiding in the construction of ground states and explaining experimental observations.

Findings

Identification of zero-energy excitations among ground states

Mapping of the magnetic problem to a two-degree-of-freedom model

Model with a specific rotation angle fits neutron data well

Abstract

Frustrated magnetic interactions in a quasi-two-dimensional [111] slab of pyrochlore lattice were studied. For uniform nearest neighbor (NN) interactions, we show that the complex magnetic problem can be mapped onto a model with two independent degrees of freedom, tri-color and binary sign. This provides a systematic way to construct the complex classical spin ground states with collinear and coplanar bi-pyramid spins. We also identify `partial but extended' zero-energy excitations amongst the ground states. For nonuniform NN interactions, the coplanar ground state can be obtained from the collinear bi-pyramid spin state by collectively rotating two spins of each tetrahedron with an angle, $\alpha$, in an opposite direction. The latter model with $\alpha \sim 30^\circ$ fits the experimental neutron data from SCGO well.