GIANT MAGNETORESISTANCE IN BULK, LIQUID-QUENCHED RIBBON AND FILM GRANULAR ALLOYS

Magnetoresistance has been investigated for bulk, liquid-quenched ribbon and film noble metal(NM)-rich granular alloys. Solid solutions were obtained in the water- , liquid- and vapor-quenched state and nano-structured magnetic precipitates in NM-rich matrix were evolved by subsequent heat treatments. After aging, the giant magnetoresistance (GMR) is observed in these bulk, liquid quenched ribbon and film granular alloys. In particular, the room temperature value of Magnetoresistance (MR) ratio of 5 % in the Co15Au85 bulk granular alloy aged at 300-degrees-C for 1 h is larger than that reported in Co/Au multilayers. The Co15Cu85 alloy ribbons aged at 500-degrees-C for 90 min exhibits the MR ratio as large as 6.3 % at room temperature in a field of 15 kOe. Small amounts of Ni improve the MR ratio. Especially, the Co15Ni5Cu85 alloy ribbons aged at 500-degrees-C for 60 min exhibits the ratio of 7.6 % larger than the value of the aged Co15Cu85 ribbon. Furthermore, the anisotropy in GMR in bulk FeNi15Cu80 alloy aged at 500-degrees-C for 170 min is obtained by compression.