The influence of Ni on the microstructure and GMR of the Co–Cu alloy granular films (abstract) : The 40th annual conference on magnetism and magnetic materials

1089-7550

AIP Digital Archive

Physics

The microstructure and Giant Magnetoresistance (GMR) in Co–Cu and Co–Ni–Cu alloy granular films prepared by dc magnetron sputtering technique was discussed. The microstructure of Co–Ni–Cu alloy granular films observed by XRD, SEM, and HRTEM examinations showed even microscopic tissue in which nanoparticles of Co–Ni were well-distributed, much different than that of Co–Cu alloy granular films in which full-grown microparticles of Co were embedded in Cu matrix. By Magnetic Hysteresis Measurement and Neel's superparamagnetism theory, the mean size of the Co–Ni particles in Co–Ni–Cu alloy granular films was estimated to be 2 to 4 nm, much smaller than that in Co–Cu alloy granular films. These results indicated that owing to the existence of Ni in Co–Ni–Cu alloy granular films the phase segregation was not a nucleation and growth process as that of Co–Cu alloy granular films but due to spinodal decomposition which was reported for the first time in granular films. It was also found that when samples dropped from room temperature to low temperature, the GMR boomed in Co–Ni–Cu alloy granular films, on the contrary to the behavior of Co–Cu alloy granular films. This fact meant that the Co–Ni–Cu alloy granular films with proper Ni content might have no response to the temperature change. Furthermore, the GMR as a function of magnetic density in Co–Ni–Cu alloy granular films is of much better linearity than that in Co–Cu alloy granular films. © 1996 American Institute of Physics.

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