Structures, Ferromagnetic Ordering, Anisotropy, and Spin Reorientation for Two- and Three-Dimensional Cyano-Bridged Mo3±-Mn2± Compounds

The compounds K2Mn3(H2O)6[Mo(CN)7]2·6H2Oand Mn2(H2O)5Mo(CN)7·nH2O (α phase, n = 4; β phase, n = 4.75) have been synthesized in the form of well shaped single crystals by slow diffusion of aqueous solutions containing [Mo(CN)7]K2·2H2O and [Mn(H2O)6](NO3), respectively. The first compound has been obtained in the presence of an excess of K± ions. The crystal structures have been determined. K2Mn3(H2O)6[Mo(CN)7]2·6H2O is two-dimensional, and Mn2(H2O)5Mo(CN)7 ·nH2O (α and β phases) are three-dimensional. The magnetic properties have been studied in great detail through single crystal magnetic measurements, and the magnetic phase diagrams have been determined. The three compounds exhibit a long-range ferromagnetic ordering along with a field-induced spin reorientation. Furtuthermore, the last two compounds show an additional magnetically ordered state which disappears when applying a suffeciently large magnetic field. The magnetic properties have been found to be dramatically modified when the non-coordinated water molecules are released. For instance, Tc is shifted from 39 to 72 K for K2Mn3(H2O)6 [Mo(CN)7]2·6H2O, and a pronounced coercivity is observed after partial dehydration.