New Ferromagnetic Chromium Chalcogenides, <i>A</i>Cr<sub>5</sub>Te<sub>8</sub> (<i>A</i> = K, Cs and Rb)

New pseudo-hollandite chromium tellurides, ACr5Te8 (A = K, Cs and Rb), have been synthesized. KCr5Te8 is isostructural (type-A; space group C2/m) to ACr5S8, while RbCr5Te8 and CsCr5Te8 crystallize in a different structure (type-B; space group C2/m). All compounds show ferromagnetic transition, in contrast to antiferromagnetic transition in pseudo-hollandite chromium sulfides and selenides. The ferromagnetism of ACr5Te8 would be related to long Cr-Cr distances, band structure or itinerancy.