The isothermal section of Tb–Dy–Co ternary system at 773K and magnetic property of (Tb1−xDyx)Co2 alloys

The isothermal section of the phase diagram of the Tb–Dy–Co ternary system at 773 K was investigated by X-ray powder diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscope (SEM). The result shows that this section consists of 9 single-phase regions and 8 two-phase regions, and no three-phase region. The compounds Tb 2 Co 17 and Dy 2 Co 17 , Tb 2 Co 7 and Dy 2 Co 7 , TbCo 3 and DyCo 3 , TbCo 2 and DyCo 2 , Tb 4 Co 3 and Dy 4 Co 3 , Tb 12 Co 7 and Dy 12 Co 7 , Tb 3 Co and Dy 3 Co form a continuous series of solid solutions. The single phases Tb and Dy also form a continuous solid solution. The binary compounds TbCo 5 and DyCo 5 were not observed at 773 K. No ternary compound was found. In addition, we experimentally determined the vertical section of pseudobinary system and magnetic property of Tb 1− x Dy x Co 2 ( x from 0 to 1) series alloys, T c decreases and the maximum magnetic entropy change |Δ S M ,max | increases with the increase of Dy content. The Arrott plots and the change of |Δ S M ,max | show that magnetic phase transition from second-order to first-order occurs with the increase of Dy content between x = 0.6 and 0.8.