Synthesis, magnetic structure, and properties of a layered cobalt-hydroxide ferromagnet, Co5(OH)6(SeO4)2(H2O)4.
The synthesis and nuclear and magnetic structures from the powder diffraction of Co(II)(5)(OH)(6)(SeO(4))(2)(H(2)O)(4) and its deuterated analogues as well as their infrared spectral, thermal, and magnetic properties are reported. The nuclear structure consists of brucite-like cobalt hydroxide layers connected by ...OSeO(3)-Co(H(2)O)(4)-O(3)SeO... bridges. The two independent cobalt atoms within the layer are arranged in chains along the b axis creating an anisotropy within each layer. The interlayer distance (10.718 A) is the only parameter to increase compared to the sulfate analogue (10.273 A). The infrared spectra and thermal properties are similar to those reported for the sulfate analogue. Due to the ferromagnetic exchange between the nearest-neighbor cobalt atoms within the layer, satisfying the Goodenough-Kanamori rule, and the weak interlayer exchange, an overall ferromagnet is obtained. The ferromagnetic order at 9 K was confirmed by the ac susceptibilities, the saturation magnetization, and most importantly the enhancement of some Bragg diffraction peaks below the Curie temperature. The moments of all the cobalt atoms were found to be aligned along the b axis with a moment of 3.25(8) mu(B) each giving the best fit. The increase in layer distance and the electron density by replacing sulfur by selenium lowers the Curie temperature.
Maalej
Wassim
W
Département Chimie des Matériaux Inorganiques, IPCMS, UMR 7504 (CNRS-UDS), 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France.
Vilminot
Serge
S
André
Gilles
G
Kurmoo
Mohamedally
M