MAGNETORESISTANCE IN AU-CO-B HETEROGENEOUS ALLOYS

Au-Co and Au-Co-B alloys have been prepared by rapid solidification, f ollowed by heat treatment. The precipitation of the ferromagnetic phas es Co and Co2B in the Au matrix phase has been observed during anneali ng. At room temperature, both magnetization and magnetoresistance are determined by the superparamagnetic behavior of the ferromagnetic part icles. The magnetoresistance is believed to have the same origin as th at in multilayers and granular films. Both Co particles and the precip itates of the Co2B intermetallic phase give rise to a high magnetoresi stance. The magnetoresistance effect was less than 1% in the as-quench ed samples and increased to about 3% after an appropriate heat treatme nt.