Scaffolds of magnetically active 3d metals in the valence electron controlled borides Ti9−xM2+xRu18B8 (M=Cr-Ni; x=0.5-1): Structutral, electronic and magnetic properties

The crystal structures of the new phases (M=Cr, Mn, Co, Ni) are confirmed by Rietveld refinement of powder diffraction data and single crystal X-ray diffraction (for M=Co) to contain beside the M-ladder also M/Ti-chains. Similar to the series Ti9M2Ru18B8, the crystal structure of the new phases are mainly stabilized by the heteroatomic Ru-B and Ru-Ti bonds that remain nearly constant throughout the series, whereas the M-containing bonds vary significantly with varying valence electron count. An experimental finding confirmed and even extended by COHP bonding analyses. In addition, the DOS analyses of the M-elements reveal the development of magnetic moments for the M=Mn, Ni cases but not for M=Co. Indeed, Ti8Co3Ru18B8 was found experimentally to be a paramagnet and ferrimagnetic ordering below 120 K is found for M=Mn.