Original magnetic behaviour observed in RNi5−xCux alloys (R = Pr, Gd or Y)

The Curie temperatures, spontaneous magnetizations and initial susceptibilities were investigated in the temperature interval from 1.5 to 40 K for the pseudobinary alloys RNi5−xCux, where R = Pr, Gd and Y, x ≤ 2.6. It was discovered that the solid solutions PrNi5−xCux between the PrNi5 and PrCu5 Van Vleck paramagnets are ferromagnets for intermediate Cu concentrations. It was shown that the ferromagnetic ordering in PrNi5−xCux alloys can be explained by concentrational enhancement of 3d band susceptibility which in its turn leads to the enhancement of f-f exchange interactions. The maxima on the concentration dependences of both Curie temperatures for the RNi5−xCux ferromagnets with R = Pr, Gd and susceptibility for the YNi5−xCux Pauli paramagnets are manifestations of 3d band magnetism.