パーマロイ磁気抵抗センサ素子の磁気的および電気的特性に及ぼす膜厚の影響

抄録

The effect of film thickness on the magnetic and electrical properties of permalloy magnetoresistive sensors is investigated. The thicknesses of permalloy thin films used are between 15 and 200 nm. The films are deposited on glass substrates by electron beam deposition and then formed into 10 μm × 50 μm patterns by photolithography.
The coercivity and the magnetic anisotropy field of the films are increased by patterning. The coercivity of patterned film increases with increasing film thickness in the range of 15 to 45 nm and decreases above 80 nm. This is because the magnetization reversal process in thinner films is caused by rotation magnetization with the buckling magnetic domain structure. While, in thicker films it is caused by the magnetic domain wall displacement. On the other hand, the magnetic anisotropy field of patterned film increases linearly with thickness, due to an increase of the demagnetizing field.
The half width of the magnetoresistive response curve and the output voltage of the magnetoresistive sensor decrease with increasing film thickness, because of the increasing demagnetizing field. Moreover, the discontinuity of output voltage due to the Barkhausen effect decreases with increasing film thickness. The Barkhausen noise is related to the occurrence and sudden extinction of buckling magnetic domains in thinner films and to the sudden movement of magnetic domain walls in thicker films.