Flux growth and magnetic properties of rare earth cobalt germanide, RE6Co5Ge1+xAl3−x (RE=Pr, Nd; x≈0.8)

• RE6Co5Ge1+xAl3−x (RE=Pr, Nd) grown as large crystals from RE/Co eutectic flux.
• RE6Co5Ge1+xAl3−x structure features hexagonal cobalt nets stacked along c-axis.
• Cobalt layers order ferromagnetically with Tc=130–140 K.
• Rare earth magnetic moments order at low temperature (30–40 K).

The intermetallic compounds RE6Co5Ge1+xAl3−x (RE=Pr, Nd) were synthesized from the reaction of germanium and aluminum in RE/Co eutectic flux. These phases crystallize with the Nd6Co5Ge2.2 structure type in hexagonal space group P-6m2 (a=9.203(2)Å, c=4.202(1) Å, R1=0.0109 for Pr6Co5Ge1.80Al2.20; and a=9.170(3) Å, c=4.195(1) Å, R1=0.0129 for Nd6Co5Ge1.74Al2.26). The structure features chains of face-sharing Ge@RE9 clusters intersecting hexagonal cobalt nets linked by aluminum atoms. Magnetic susceptibility measurements indicate that both phases exhibit ferromagnetic ordering of the cobalt layers with TC in the range of 130–140 K. The magnetic moments of the rare earth ions order at lower temperature (30–40 K). Magnetic measurements on oriented crystals of Nd6Co5Ge1.74Al2.26 show a strong preference of the moments to order along the c-axis.

RE6Co5Ge1+xAl3−x (RE=Pr, Nd) were grown as large crystals from reactions of Ge and Al in RE/Co eutectic melts. Magnetic measurements indicate ordering of the 2-D cobalt nets at 130–140 K, and ordering of the rare earth moments at 30–40 K.Figure optionsDownload as PowerPoint slide