Structural and magnetic properties of Pr2Co7 powders

Abstract

The Pr2Co7 intermetallic compounds are known to crystallize in two polymorphic forms. A hexagonal of the Ce2Ni7 type structure and a rhombohedral of the Gd2Co7 type structure were obtained by mechanical milling and subsequent annealing in high vacuum. The highest intrinsic coercivity value 18 kOe at room temperature and magnetization ratio (Mr/Mmax = 0.64) were determined for alloys milled during 5 h and annealed at 800°C for 30 min. The enhanced remanence (Mr/Mmax > 0.50) suggests strong exchange interaction between the adjacent crystallites. This is in good agreement with the small average crystallite size (D ≈ 50 nm). The high magnetic properties observed in these nanostructured Pr2Co7 intermetallic alloys have their origin in its relatively high uniaxial magnetocrystalline anisotropy field, and in the homogeneous nanostructure developed by mechanical milling process and subsequent annealing.