The isothermal section of Tb-Dy-Co ternary system at 773 K 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 Tb2Co17 and Dy2Co17, Tb2Co7 and Dy2Co7, TbCo3 and DyCo3, TbCo2 and DyCo2, Tb4Co3 and Dy4Co3, Tb12Co7 and Dy12Co7, Tb3Co and Dy3Co form a continuous series of solid solutions. The single phases Tb and Dy also form a continuous solid solution. The binary compounds TbCo5 and DyCo5 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 Tb1−xDyxCo2 (x from 0 to 1) series alloys, Tc decreases and the maximum magnetic entropy change |ΔSM,max| increases with the increase of Dy content. The Arrott plots and the change of |ΔSM,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.