Tunable magnetic order in low-symmetry SeO$_3$ ligand linked $TM_3$(SeO$_3$)$_3$H$_2$O ($TM$ = Mn, Co and Ni) compounds

TL;DR

This study explores how changing transition metal ions in SeO$_3$-linked compounds affects their magnetic order, revealing tunable antiferromagnetic structures and proximity to metamagnetic states, with potential for designing frustrated magnetic materials.

Contribution

It demonstrates the magnetic tunability in SeO$_3$-linked TM compounds through experimental and theoretical analysis, highlighting the influence of TM site variation on magnetic properties.

Findings

All three compounds show low-temperature antiferromagnetic order.

Magnetic structure is sensitive and tunable by changing the TM ion.

Metamagnetic transitions observed in Mn and Co compounds.

Abstract

Generally, one has two strategies to achieve magnetic frustration: through geometric means or interactions with different length scales. As the former leads to much simpler theoretical treatments it is favored and so magnetic sublattices with geometric frustration are sought after. One approach to finding such lattices is to design them chemically by using non-magnetic linker ligands. Here we report on the magnetic properties of one such family of materials, the transition metal ($TM$) selenite hydrate compounds chemical formula $TM_3$(SeO$_3$)$_3$H$_2$O . These materials link highly distorted $TM$O$_6$ octahedra via non-magnetic [SeO$_3$]$^{2+}$ linkers. Using $TM$ = Mn, Co and Ni we report on the structural effects of changing the $TM$ site and how they may influence the magnetic structure. Using magnetic susceptibility and neutron powder diffraction we identify low temperature magnetic transitions for all three compounds characterized by the onset of long-range AFM order with moderate frustration indexes. Consideration of the magnetic structures reveal that the magnetic order is sensitive to the $TM$ site ion and is tunable as it is changed - especially from Mn to Co - with changes in both the moment direction and the ordering vector. Field dependent susceptibility and heat capacity measurements reveal metamagnetic transitions in both Mn$_3$(SeO$_3$)$_3$H$_2$O and Co$_3$(SeO$_3$)$_3$H$_2$O indicating nearby magnetic ground states accessible under relatively small applied fields. Density functional theory calculations broadly confirm these results, showing both a sensitivity of the magnetic structure to the $TM$ and its local environment. Although no spin liquid behavior is achieved, these results suggest the fruitfulness of such synthesis philosophies and encourage future work to engender higher frustration in these materials via doping, field, pressure or larger linker ligands.