Magnetic properties of image compounds image

In the present work the synthesis and magnetic properties of three compounds with formula image image are described. These compounds are synthetic analogs to natural occurring minerals: fenaksite—image, litidionite—image and manaksite—image. The crystal structure consists of complex silicate chains interconnected by edge-sharing image square pyramids dimerized in image units. This charged metal–silicate framework is compensated by monovalent alkali metals (image, image). Despite the isostructural nature of these compounds, and the consequent similarity of the M–O topology, that rules the magnetic properties, these are quite different. While there are antiferromagnetic (AF) interactions within the Mn and Cu dimers (exchange interaction image and image, respectively) with no long range order, a ferromagnetic interaction within Fe dimers image is observed with a three-dimensional transition at 9 K to an AF ground state. The magnetic behavior is analyzed using the HDVV (Heisenberg–Dirac–Van Vleck) formalism and discussed in the light of the crystal structure.