Studies on the Magnetic Ground State of a Spin M\"obius Strip

TL;DR

This study synthesizes and characterizes vanadium-based ring structures, revealing antiferromagnetic interactions that lead to distinct magnetic ground states depending on the ring size, with implications for understanding spin frustration.

Contribution

It reports the synthesis and detailed magnetic characterization of novel vanadium-sodium cyclic structures with unique ground state properties.

Findings

Even-membered rings have S=0 ground states due to antiferromagnetic interactions.

Heptanuclear cluster exhibits spin frustration with quasi-degenerate S=1/2 states.

Structural analysis shows alternating vanadium and sodium ions separated by O-Na-O groups.

Abstract

Here we report the synthesis, structure and detailed characterisation of three n-membered oxovanadium rings, Na$_n$[(V=O)$_n$Na$_n$(H$_2$O)$_n$($\alpha$, $\beta$, or $\gamma$-CD)$_2$]$m$H$_2$O (n = 6, 7, or 8), prepared by the reactions of (V=O)SO$_4$$\cdot$$x$H$_2$O with $\alpha$, $\beta$, or $\gamma$-cyclodextrins (CDs) and NaOH in water. Their alternating heterometallic vanadium/sodium cyclic core structures were sandwiched between two CD moieties such that O-Na-O groups separated neighbouring vanadyl ions. Antiferromagnetic interactions between the $S$ = 1/2 vanadyl ions led to $S$ = 0 ground states for the even-membered rings, but to two quasi-degenerate $S$ = 1/2 states for the spin-frustrated heptanuclear cluster.