MAGNETISM OF PR2(FE1-X-YCOXALY)17 ALLOYS WITH A TH2ZN17-TYPE STRUCTURE

Alloys with the composition Pr2(Fe1-xCo x)17-yAly have been synthesized by the arc-melting technique followed by 125-h annealing at 900 °C in evacuated silica capsules. From room-temperature x-ray powder diffraction analysis a complete solid solution Pr2(Fe1-xCox) 17-yAly has been observed for all values of 0≤x≤1 and 0≤y≤5.1. All alloys were found to crystallize with the Th 2Zn17-type structure; Al atoms tend to preferentially occupy the (6c) sites. Fe/Co substitution generally leads to an increase of the Curie temperature and of the magnetocrystalline anisotropy, thereby enhancing the remanence as well as the coercivity. These effects are predominantly due to the strongly distant-dependent exchange interactions of the Fe-Fe(Co) and the Fe(Co)-rare-earth coupling mechanism. Whereas most of the alloys exhibit easy-plane magnetism, a small range exists in the Pr 2(Fe1-xCox)17-yAly system (0.38<x<0.82, 300 K), in which the crystallographic c axis is the direction of easy magnetization. Small amounts of Al, however, close the easy-axis region at y=1.8 (∼300 K).