Peculiarities of permalloy thin film microcore hysteretic magnetization process in high space resolution fluxgate device

Magnetization processes of the sectioned thin film permalloy core were examined in relation with its geometrical dimensions using magnetooptical Kerr technique and ferrofluid observation. It is shown quantitatively the intermediate case between Stoner-Wohlfarth and zero internal field contradicting models takes place. Ferrofluid investigation had shown the stable quasi-saturated state with closing domain structures at permalloy bar edges. Magnetization reversal occurs by hysteretic manner but the hysteresis loop parameters are reproducible and depend strongly upon core geometry. Hysteresis is characterized by parallelogram form with clear critical field and loop slope depending on bars dimensions and their mutual position in array. Loop shape approaches the rectangular form and critical field increases if bar thickness t, width w and bar density in array are decreased. The critical field value Hcr is defined by demagnetizing field at bar edges while the saturation field Hs depends only on width w at of a bar in array. Variation of the bar form or shift of every second bar in array possesses to increase the core thickness to enhance the stray field without increase of the saturating exciting current. The core described can be used with magnetooptical garnet film or Hall sensor in fluxgate regime for magnetic field measurement with space resolution 10-100 mcm.