HfCo₇-Based Rare-Earth-Free Permanent-Magnet Alloys

This study presents the structural and magnetic properties of melt-spun HfCo7,HfCo7-xFex(0.25 ≤ × ≤ 1) and HfCo7Six(0.2 ≤ × ≤1.2) alloys. Appreciable permanent-magnet properties with a magnetocrystalline anisotropy of about 9.6-16.5 Mergs/cm3, a magnetic polarization Js≈ 7.2-10.6 kG, and coercivities Hc= 0.5-3.0 kOe were obtained by varying the composition of these alloys. Structural analysis reveals that the positions of x-ray diffraction peaks of HfCo7show good agreement with those corresponding to an orthorhombic structure having lattice parameters of about α = 4.719 Å, b = 4.278 Å, and c = 8.070 Å. Based on these results, a model crystal structure for HfCo7is developed and used to estimate the magnetic properties of HfCo7using density-functional calculations, which agree with the experimental results.