Crystal chemistry and magnetic properties of the solid solutions Ca 14-x RE x MnBi 11 (RE = La-Nd, Sm, and Gd-Ho; x ≈ 0.6-0.8).

The new solid solutions Ca14-x REx MnBi11 (RE = La-Nd, Sm, and Gd-Ho; x ≈ 0.6-0.8) were prepared by using a Pb-flux technique and structurally characterized by single-crystal X-ray diffraction. All synthesized materials crystallize in the tetragonal Ca14 AlSb11 structure type (space group: I41 /acd, Pearson index: tI208). The magnetic responses of all the members of the series were investigated, and for all REs in this study, except for Sm, a ferromagnetic ordering was observed at TC = 35-44 K. The Sm-containing sample shows a ferromagnetic-like transition at 40 K and enters a long-range antiferromagnetic state below 17 K. The magnetic behavior of Ca14-x REx MnBi11 differs from that of the isostructural Ca14-x REx MnSb11 series, emphasizing the importance of the weak magnetic interactions in complex crystal structures.