Entail the new path for permanent magnets: Free-standing Hf-Co thin films

In this work, as an alternative to permanent magnets containing rare earth, we report a method for the preparation of rare-earth-free (REF) free-standing magnetic thin films have been obtained by using a basis sacrificial layer with magnetron sputtering technique. Stoichiometric Hf34.5Co65.5 thin films are deposited on sacrificial layer coated on Si(100) substrate and removed by a selective wet-chemical etching method. Conditions for the crystallization of Hf2Co11 magnetic thin films are indicated. No crystalline peaks are found in the XRD pattern of the as-deposited film, remarking an amorphous structure. The formation of the hard magnetic orthorhombic Hf2Co11 phase requires a post-annealing at 773 K or higher until at 923 K. Freestanding Hf2Co11 thin film, which is post-annealed at 923 K, has following permanent magnet properties; Hc = 6 kOe, Mr = 370 emu.cm−3, (BHi)max = 6.6 MGOe.