Crystal structure and magnetic properties of the RCu3Te3 (R = Er and Tm) compounds

The crystal structures of the RCu3Te3 (R = Er and Tm) compounds (space group Pmn21, Pearson symbol oP28) were determined by means of X-ray powder diffraction: a = 1.26784(6) nm, b = 0.76161(3) nm, c = 0.69016(3) nm, RBragg = 0.0814 for ErCu3Te3; a = 1.26756(3) nm, b = 0.76053(2) nm, c = 0.69034(2) nm, RBragg = 0.0639 for TmCu3Te3. The Te atoms are stacked in a close-packed arrangement with layers in the sequence AB. The R atoms occupy one-third of octahedral interstices, whereas the Cu atoms occupy half of tetrahedral interstices. Both compounds are Curie–Weiss paramagnets with no magnetic ordering down to 1.9 K.