The giant magnetoresistance (GMR) effect of nanogranular Ag 72Co 28 thin films made by an rf magnetron sputtering method on a glass substrate has been examined as a sensor having high temperature durability for brushless dc motors. In the temperature dependence, the MR ratio of nanogranular Ag 72Co 28 thin film in 10 kOe is 13% at room temperature and decreases to 4% at 573 K. On the other hand, the room temperature MR ratio of 10% was obtained by isothermal aging at 773 K for 7.2 ks or at 673 K for 100 ks. From the Arrhenius plots for the aging time versus the aging temperature, the durability of the GMR effect at 473 K is estimated to be ten years. The nanogranular Ag 72Co 28 film having 4% of the GMR effect set in the motor can accurately detect the rotating angle of the rotor from the quiescent state to the rotating state of 3000 rpm. This means that nanogranular Ag 72Co 28 films prepared under various conditions are suitable for sensors working at high temperatures. Consequently, the nanogranular Ag 72Co 28 films have a high potential for the higher output power of the brushless dc motors.
ASJC Scopus subject areas
- Physics and Astronomy(all)