Magnetic transitions in the cyano-bridged bimetallic ferromagnet Mn2(H2O)5Mo(CN)7•4.75H2O (β phase)

Slow diffusion of two aqueous solutions containing K-4[Mo(CN)(7)]. 2H(2)O and [Mn(H2O)(6)](NO3)(2), respectively, has afforded two kinds of single crystals whose formulas are Mn-2(H2O)(5)Mo(CN)(7)]. 4H(2)O (alpha phase) and Mn-2(H2O)(5)Mo(CN)(7)]. 4.75H(2)O (beta phase). This paper is devoted to the latter compound. It crystalizes in the monoclinic system, space group P2(1)/c, a = 7.885(3) Angstrom, b = 10.406(7) Angstrom, c = 25.233(11) Angstrom, beta = 98.11(2)degrees, Z = 4. The Mo site is surrounded by seven -C-N-Mn linkages in a distorted pentagonal bipyramid fashion. There are two distorted octahedral Mn sites, one with four and the other with three -N-C-Mo linkages. The structure is three-dimensional. It consists of bent ladders made of edge-sharing (MoCNMnNC)(2) lozenge motifs running along the a direction. These ladders are linked further along the a and c directions. The a, b, and c* axes were determined to be the magnetic axes; Both temperature and field dependence of the magnetization have been measured along the magnetic axes. The angular dependence of the magnetization in the ab plane as a function of the external field has also been measured. Single crystal magnetic measurements revealed that the compound orders ferromagnetically at T-c = 51 K, without a hysteresis effect. They have also shown that the compound has a complex magnetic phase diagram when the field is applied along the a direction, with several ferromagnetically ordered domains and a spin reorientation domain. The boundaries between these domains have been determined. These results have been compared to those obtained with Mn-2(H2O)(5)Mo(CN)(7)]. 4H(2)O (alpha phase).