Phase Transitions in the Pseudo-Binary Compounds Ho1-xTbxB2C2

Abstract

We have performed specific heat experiments on Ho 1- x Tb x B 2 C 2 (0≤ x ≤1.0) in order to clarify the similarity and difference between anomalous antiferromagnetic phases of HoB 2 C 2 and TbB 2 C 2 . HoB 2 C 2 undergoes an antiferromagnetic (AFM) transition at T N =5.9 K and an antiferroquadrupolar (AFQ) transition at T Q =4.5 K. TbB 2 C 2 shows only an AFM transition at T N =21.7 K. Although T N changes gradually with increasing x , T Q hardly decreases up to x =0.6. This unusual result indicates that the Tb atoms seem to support the AFQ order in HoB 2 C 2 . However, judging from an entropy change at T Q , it is supposed that the Tb atoms do not participate in the AFQ order.