High coercivity and giant magnetoresistance of CoAg, CoCu granular films

• Published in: Journal of magnetism and magnetic materials 2007-03, Vol.310 (2), p.2524-2526
• Main Authors: Hiep, V.V., Chau, N., Hong, D.M., Luong, N.H.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Diamagnetism, paramagnetism and superparamagnetism; Exact sciences and technology; Giant magnetoresistance; Magnetic properties and materials; Magnetotransport phenomena, materials for magnetotransport; Metal nanoparticle; Nanogranular alloy; Physics; Superparamagnetism; Thin film
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2006.11.136

We report our study on the structure, magnetic and giant magnetoresistance properties of two systems: Co x Ag 1− x ( x=33, 48, 49, 52 at%) and Co y Cu 1− y ( y=11, 13, 15, 17 at%) granular films prepared by RF sputtering. The thermal transition measured by the SDT 2960 apparatus revealed exothermal peaks at 400 °C, corresponding to the crystallization of FCC-Co crystallites. The studied films were annealed in a temperature range of 300–450 °C for 1 h. The structure and particle size were determined from the X-ray diffraction data. Superparamagnetic state was shown in as-deposited films. After appropriate heat treatment, coercivity increased up to 1100 Oe in the Co 52Ag 48 film annealed at 350 °C, and 690 Oe in the Co 13Cu 87 film annealed at 400 °C. Maximum magnetoresistance up to 4.25% in the Co 48Ag 52 film, and 5.4% in the Co 15Cu 85 film annealed at 400 °C was obtained. Our values for magnetoresistance are quite high compared with recent studies.