Rare-earth chromium gallides RE4CrGa12 (RE=Tb–Tm)

The ternary rare-earth-metal chromium gallides RE 4CrGa12 (RE =Tb–Tm) have been prepared by reactions of the elements at 1000 °C in the presence of excess gallium used as a self-flux. Their structures are derived by inserting Cr atoms into a quarter of the empty Ga6 octahedral clusters found in the parent binary gallides RE Ga3 (AuCu3-type), although single-crystal X-ray diffraction studies suggest that complex superstructures may be adopted. An ideal ordered Y4PdGa12-type structure was successfully refined for a crystal of Dy4CrGa12 (Pearson symbol cI 34, space group Im View the MathML source3¯m, Z=2, a=8.572(1) Å). Magnetic measurements on single-crystal samples reveal ferromagnetic or possibly ferrimagnetic ordering for the Tb, Dy, and Er members (TC=22, 15, and 2.8 K, respectively) and antiferromagnetic ordering for the Ho member (TN=7.5 K). Band structure calculations on a hypothetical “Y4CrGa12” model suggest that the Cr atoms carry no local magnetic moment.