Crystal structure and physical properties of shchurovskyite-related K2CaCu6O2(PO4)4

Abstract

A new oxocuprate phosphate, K₂CaCu₆O₂(PO₄)₄, was obtained as tabular dark-green single crystals through flux-assisted high-temperature synthesis. It crystallizes in the space group P2/c and represents the centrosymmetric modification of the fumarolic arsenate mineral shchurovskyite, K₂CaCu₆O₂(AsO₄)₄. The crystal structure of the compound under study is characterized by the presence of large channels filled with potassium cations. Bond-valence energy landscape calculations based on structural data showed the probability of K⁺ migration through the crystal structure along the b axis at an energy of 0.6 eV. K₂CaCu₆O₂(PO₄)₄ ordered into a canted antiferromagnetic state in two steps at T_N1 = 22 ± 2 K and T_N2 = 10 ± 1 K, as revealed by magnetization and specific heat measurements.