A unique two-dimensional silver(II) antiferromagnet Cu[Ag(SO4)2] and perspectives for its further modifications

TL;DR

This study investigates the structure, magnetic properties, and potential modifications of a novel two-dimensional silver(II) antiferromagnet, Cu[Ag(SO4)2], revealing its layered magnetic interactions and possibilities for substitution with other cations.

Contribution

It provides the first detailed characterization of Cu[Ag(SO4)2]'s structure, magnetic behavior, and theoretical insights into its superexchange interactions and substitution potential.

Findings

Cu[Ag(SO4)2] is an antiferromagnet with ordering at 19 K and 40 K.

Layered [Ag(SO4)2]2- structures facilitate strong 2D antiferromagnetic coupling.

Density functional theory shows potential for substituting Ag2+ with other cations.

Abstract

Copper(II) silver(II) sulfate crystallizes in a monoclinic CuSO4-related structure with P21/n symmetry. This quasi-ternary compound features [Ag(SO4)2]2- layers, while the remaining cationic sites may be occupied either completely or partially by Cu2+ cations, corresponding to the formula of (CuxAg1-x)[Ag(SO4)2], x = 0.6-1.0. CuAg(SO4)2 is antiferromagnetic with large negative Curie-Weiss temperature of -84.1 K and shows two characteristic ordering phenomena at 19 K and 40 K. Density functional theory calculations reveal that the strongest superexchange interaction is a two-dimensional antiferromagnetic coupling within [Ag(SO4)2]2- layers, with the superexchange constant J2D of -11.1 meV. This renders CuAg(SO4)2 the rare representative of layered Ag2+-based antiferromagnets. Magnetic coupling is facilitated by the strong mixing of Ag d(x2-y2) and O 2p states. Calculations show that M2+ sites in MAg(SO4)2 can be occupied with other similar cations such as Zn2+, Cd2+, Ni2+, Co2+, and Mg2+.