High-Pressure Torsion for Giant Magnetoresistance and Better Magnetic Properties

• Published in: Advanced engineering materials 2010-08, Vol.12 (8), p.793-797
• Main Authors: Nishihata, Shingo, Suehiro, Kenichiro, Arita, Makoto, Masuda, Masataka, Horita, Zenji
• Format: Article
• Language: English
• Subjects: Alloys; Coercive force; Electron probes; Ferromagnetism; Giant magnetoresistance; Magnetic properties; Saturation (magnetic); Torsion
• ISSN: 1438-1656; 1527-2648; 1527-2648
• DOI: 10.1002/adem.201000033

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. Two‐phase Cu‐10%Co and Cu‐22%Fe alloys were subjected to high‐pressure torsion (HPT) and ferromagnetic Co and Fe phases were significantly refined with straining by HPT. Because of a fine dispersion of the ferromagnetic phases, magnetoresistance with an isotropic feature corresponding to giant magnetoresistance (GMR) appears at room temperature. HPT can be a potential process for creating GMR in the alloys prepared by conventional ingot metallurgy.