Crystal Structure and Magnetic and Magnetocaloric Properties of Cobalt Hydroxychlorides Co2(OH)4–xClx

• Published in: European journal of inorganic chemistry 2017-04, Vol.2017 (16), p.2289-2294
• Main Authors: Song, Sang‐Hoon, Alonso, José Antonio, Fernández‐Díaz, María Teresa, Lim, Sang Ho
• Format: Article
• Language: English
• Subjects: Cobalt; Crystal structure; Diffraction; Magnetic frustration; Magnetic properties; Structure elucidation; Transition metals
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201700104

A series of isostructural cobalt hydroxychloride salts with the formula Co2(OH)4–xClx were fabricated by using a precipitation method from aqueous solutions of CoCl2 and NaOH with different mixing ratios. The crystal structure was resolved from neutron powder diffraction data, including the location of H atoms of the hydroxide groups. The structure (space group R3m) consists of an open network of edge‐sharing CoO6 and CoO6–2xCl2x octahedra, forming intercrossed 1D channels where the hydrogen atoms reside. Unusually high values of the magnetic entropy change were observed for all samples, probably due to the geometrically frustrated magnetic structure; for example, the magnetic entropy change was 8.3 J/kg K for the sample with Co/Cl > 2.5 at 10 K in a magnetic field change of 20 kOe. A neutron powder diffraction study of Co2(OH)4–xClx reveals that edge‐sharing CoO6 and CoO6–2xCl2x octahedra form intercrossed 1D channels where the hydrogen atoms reside. Variations of the magnetic and magnetocaloric properties with the Co/Cl ratio are correlated with the atomic arrangement of OH– and Cl– around the Kagomé Co2+ ions.