Anisotropy induced anomalies in Dy_1−xTb_xAl₂

The Dy_1−xTb_xAl₂ alloys have been investigated by X-ray powder diffraction, heat capacity, and magnetic measurements. All samples exhibit cubic Laves phase crystal structure at room temperature but at T_C, DyAl₂ and TbAl₂ show tetragonal and rhombohedral distortions, respectively. First order phase transitions are observed below T_C (at the spin-reorientation transition, T_SR) in the alloys with 0.15 ≤ x ≤ 0.35. These transitions are signified by sharp heat capacity peaks and corresponding anomalies in the magnetization and ac magnetic susceptibility data. The observations are interpreted by taking into consideration the differences in easy magnetization directions of DyAl₂ and TbAl₂. Due to the competing magnetic structures, the anisotropy-related instability and magnetic frustrations are prominent in the Dy_1−xTb_xAl₂ alloys at certain concentrations resulting in the first order transitions.