Synthesis and magnetic properties of Pr(Fe1-xCox)2 and Pr1-yTby(Fe0.4Co0.6)2 alloys

Measurement of X-ray diffraction, magnetization and magnetostriction was made on the Pr(Fe1-xCox)2 (x=0.4, 0.5 and 0.6) and Pr1-yTby(Fe0.4Co0.6)2 (y=0, 0.1, 0.2 and 0.3) alloy series. It was found that a cubic phase with the MgCu2 structure can be obtained in the Pr(Fe1-xCox)2 series only at x=0.6. The Pr1-yTby(Fe0.4Co0.6)2 system has the cubic MgCu2 structure over the studied range for y. The lattice constant and magnetization decrease and the Curie temperature increases with increasing y. At 7 K, Pr1-yTby(Fe0.4Co0.6)2 samples are found to have huge intrinsic coercivities, which are associated with narrow domain walls. It is also found from X-ray measurement that in Pr1-yTby(Fe0.4Co0.6)2 the spontaneous magnetostriction λ111 increases due to Tb substitution, while the saturation magnetostriction λs is much lower than λ111. This can be attributed to the large value of λ100 with an opposite sign to λ111, which may be caused by the filling of the d band due to Co substitution.