A Unique Two‐Dimensional Silver(II) Antiferromagnet Cu[Ag(SO4)2] and Perspectives for Its Further Modifications

Abstract

AbstractCopper(II) silver(II) sulfate crystallizes in a monoclinic CuSO4‐related structure with P21/n symmetry. This quasi‐ternary compound features Ag(SO4)22− 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 −140 K and shows characteristic ordering phenomenon at 40.4 K. Density functional theory calculations reveal that the strongest superexchange interaction is a two‐dimensional antiferromagnetic coupling within Ag(SO4)22− 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+.