Ca_25Co_22O_56(OH)_28: a layered misfit compound

TL;DR

This study reports the synthesis, structure, and magnetic properties of a layered misfit compound Ca_25Co_22O_56(OH)_28, revealing its unique misfit structure, magnetic behavior, and absence of superconductivity down to 2K.

Contribution

It provides detailed characterization of a new misfit layered compound, including its structure and magnetic properties, expanding understanding of such materials.

Findings

Crystallizes in monoclinic space group C2/m

Displays Curie-Weiss paramagnetism with antiferromagnetic Weiss temperature

No superconductivity observed down to 2K

Abstract

The high pressure synthesis, structure and magnetic properties of Ca_25Co_22O_56(OH)_28 are reported. The compound has a misfit structure, consisting of double, square calcium oxide hydroxide rock-salt-like layers between hexagonal CoO_2 layers. The misfit compound crystallizes in the monoclinic space group C2/m, and can be characterized by the coexistence of two subsystems with common a=4.893(5)A, c=8.825(9)A and b=95.745(8) parameters, and different b parameters: b_RS=4.894(5)A, and b_HEX=2.809(3)A, for the rock-salt and hexagonal type planes respectively. The compound shows Curie-Weiss paramagnetism with an antiferromagnetic Weiss temperature of -43K and a reduced Co moment. Substantial deviations from Curie-Weiss behavior are seen below 50K with no indication of magnetic ordering. No superconductivity was observed down to a temperature of 2K.