High‐Pressure Torsion for Giant Magnetoresistance and Better Magnetic Properties

Abstract High‐pressure torsion (HPT) was conducted on Cu alloys containing ferromagnetic Co and Fe particles. Electron probe microanalysis, X‐ray diffraction analysis, and transmission electron microscopy confirmed that the particles were significantly refined through fragmentation and some fractions were dissolved into the Cu matrix with straining by HPT. Saturation magnetization decreases with straining and coercive force increases with straining but they level off after intense straining. Magnetoresistance with an isotropic feature corresponding to giant magnetoresistance (GMR) appears at room temperature by processing with HPT. It is demonstrated that HPT is a potential process for controlling magnetic properties such as saturation magnetization and coercive force and also for creating GMR in the alloys prepared by conventional ingot metallurgy.