Nd8Co4−xAlxGe2C3: A case study in flux growth of lanthanide-rich intermetallics

• Nd8Ge2Co3.35Al0.65C3 grows as large crystals from reactions in Nd/Co eutectic flux.
• Structure features Ge@Nd9 clusters and zigzag cobalt chains capped by carbon.
• Cobalt has no magnetic moment; Nd3+ ion moments order ferromagnetically.
• Hard ferromagnet with strong anisotropy below TC of 50 K.
• Flux growth and structural trends of lanthanide-rich intermetallics are reviewed.

The intermetallic Nd8Co4−xAlxGe2C3 (x≈0.65) was prepared from reaction of germanium and carbon in Nd/Co eutectic flux in an alumina crucible. This phase exhibits a new structure type in orthorhombic space group Pbcm, with unit cell parameters a=8.001(1) Å, b=11.696(2) Å, c=15.020(3) Å (Z=4; R1=0.0234). The structure features germanium-centered neodymium clusters Ge@Nd9 which share faces to form layers separated by zigzag chains of cobalt atoms capped by carbon. Density of states calculations confirm that this compound is metallic, and indicate that the cobalt should not have a magnetic moment. This is supported by magnetic susceptibility measurements which show a low temperature ferromagnetic ordering at TC=50 K due to the Nd3+ ions. Magnetization field dependence studies on single crystals indicate this compound is a strong ferromagnet with large anisotropy; the Nd3+ magnetic moments align along the a-axis.

Nd8Co4−xAlxGe2C3 (x≈0.65) contains germanium-centered neodymium clusters Ge@Nd9 which share faces to form layers separated by zigzag chains of cobalt atoms capped by carbon.Figure optionsDownload as PowerPoint slide