Magnetic Phase Diagrams of Dy0.8Gd0.2B2C2 with the Antiferroquadrupolar Ordering in the Antiferromagnetic Phase

Abstract

Gd substitution for Dy in DyB 2 C 2 that undergoes an antiferroquadrupolar (AFQ) ordering at T Q =24.7 K and an antiferromagnetic (AFM) one at T N =15.3 K enhances the AFM interaction and weakens the AFQ interaction. In Dy 0.8 Gd 0.2 B 2 C 2 , the AFQ transition occurs at T Q =17.6 K below the AFM one at T N =19.0 K. However, the strong competition between the AFQ and AFM interactions supresses the development of the AFQ order parameter below T Q and causes an anomalous behavior in field-induced transitions. The magnetic phase diagrams of Dy 0.8 Gd 0.2 B 2 C 2 drawn from the experimental results of specific heat and magnetization have anomalous phase boundaries originating from this competition.