Influence of Tb on easy magnetization direction and magnetostriction of PrFe_1.9 alloy

The crystal structures, magnetization, and spontaneous magnetostriction of ferromagnetic Laves phase Pr_1-xTb_xFe_1.9 compounds are investigated in a temperature range between 5 K and 300 K. High resolution synchrotron x-ray diffraction (XRD) analysis shows that different proportions of Tb in Pr_1-xTb_xFe_1.9 alloys can result in different easy magnetization directions (EMD) below 70 K, i.e.,100 with x=0.0, and111 with x ≥ 0.1. This indicates Tb substitution can lead the EMD to change from100 to111 with x rising from 0.0 up to 0.1. The Tb substitution for Pr reduces the saturation magnetization M_s and the magnetostriction to their minimum value when x=0.6, but it can increase low-field (0 ≤ H ≤ 9 kOe, the unit 1 Oe=79.5775 A·m^-1) magnetostriction when x=0.8 and 1.0 at 5 K. This can be attributed to the larger magnetostriction of PrFe_1.9 than that of TbFe_1.9, as well as the decrease of the resulting anisotropy due to Tb substitution at low temperatures.