MAGNETO-IMPEDANCE IN SPUTTERED AMORPHOUS FILMS FOR MICRO MAGNETIC SENSOR

The magneto-impedance (MI) effect in RF sputtered (CoFe)(80)B-20 zero-magnetostrictive amorphous films are presented, The relation between annealing conditions and MI characteristics was investigated. Impedance Z monotonously decreased with increasing applied field Hex when a high frequency sinusoidal current was applied to the sample annealed in a rotational field. In case of the samples having transverse anisotropy, Z sharply increases with Hex for the region Hex < Hk (anisotropy field). MI ratio ((Delta\Zl/\Z(0)\/Oe) of 8%/Oe was obtained for the sample annealed in a dc field (or applying dc current) after annealing in the rotational field. The Colpitts oscillator type field sensor was constructed using the film element. A direction sensing utilizing the terrestrial field was carried out using the MI-colpitts sensor.