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

Abstract

A new phosphate K₂CaCu₆O₂(PO₄)₄ has been obtained in the form of tabular dark-green single crystals through the high-temperature synthesis in the flux. It crystallizes in a space group P2/c and represents a 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 occupied by 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 orders into canted antiferromagnetic state in two steps at T_N1 = 22 ± 2 K and T_N2 = 10 ± 1 K, as revealed in magnetization and specific heat measurements.