Magnetic fields associated with thin nickel-iron films

Abstract

This paper describes the external magnetic field of a thin, circular, single domain, magnetic film both experimentally and analytically. Measurements and calculations of the spatial components of flux in sense loops about nickel-iron films have been made as the sense loops are moved in specified directions relative to the film. The calculations are made on the assumption that the magnetic field of the thin film is the same as that of an oblate spheroid with uniform magnetization in the plane of the film Measurements have been made on three, 1.59-cm-diam, circular, evaporated films with different characteristics in regards to composition ratio and thickness. The thickness-to-diameter ratio of these films is on the order of 10-5. Comparison between measurements and calculations shows good agreement both in magnitude and functional dependence, indicating that the field of an oblate spheroid is a good approximation to that of a thin film. One major discrepancy is that the measured component of field in a direction in the plane of the film, but perpendicular to the magnetization, was approximately a factor of two larger than the calculated values, thus showing the limitations of the spheroid approximation. The results are presented as normalized curves; therefore, the results are applicable to any film whose thickness-to-diameter ratio is very small. © 1964 The American Institute of Physics.