Understanding complex magnetic order in disordered cobalt hydroxides through analysis of the local structure

Abstract

In many ostensibly crystalline materials, unit-cell-based descriptions do not always capture the complete physics of the system due to disruption in long-range order. In the series of cobalt hydroxides studied here, Co(OH)${}_{2-x}$(Cl)${}_x$(H${}_2$O)${}_n$, magnetic Bragg diffraction reveals a fully compensated Néel state, yet the materials show significant and open magnetization loops. A detailed analysis of the local structure defines the aperiodic arrangement of cobalt coordination polyhedra. Representation of the structure as a combination of distinct polyhedral motifs explains the existence of locally uncompensated moments and provides a quantitative agreement with bulk magnetic measurements and magnetic Bragg diffraction.