Influence of demagnetizing effects on the magnetization curves of finite-size rectangular slabs

Abstract According to some recent studies, the magnetoresistance curves of ferromagnetic strip-shaped samples can significantly differ depending on whether the in-plane external applied magnetic field H is oriented in parallel to either the long or the short edge of the strip. To address this problem, in the present work magnetization curves M ( H ) were measured for similarly shaped samples with both magnetic field orientations used in the magnetoresistance measurements. It was found that the M ( H ) curves strongly depend on the saturation magnetization and shape of the samples as well as on the magnetic field orientations. For some samples with sufficiently large saturation magnetization, the effective demagnetizing factors could be deduced from the measured M ( H ) curves. By considering the investigated samples as a ferromagnetic slab, and approximating them with a general ellipsoid, the demagnetizing factors were calculated from known formulae and compared to the experimental values. A fairly good matching was observed, although the latter data were systematically slightly larger, certainly due to the not completely homogeneous magnetization within the rectangular slab as opposed to the case of a general ellipsoid. The differences in the M ( H ) curves for the two orientations of the magnetic field could be completely attributed to demagnetizing effects.