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, R(Bragg) =0.0814 for ErCu3Te3; a = 1.26756(3) nm, b = 0.7605 3(2) nm, c=0.69034(2) nm, R(Bragg) = 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.