Steady-State B-H Hysteresigraph for Thin Ferromagnetic Films Using a Torque Magnetometer

Abstract

An ordinary torque magnetometer can be used to obtain dc B‐H hysteresis loops of thin ferromagnetic films simply by replacing the rotating set of Helmholtz coils with a stationary set of three mutually perpendicular coils and by mounting the film edgewise on the suspension. When the magnetometer is used in this mode, the signal and signal‐to‐noise ratio are directly proportional to the field normal to the film; thus one can measure the anisotropy field of film samples many times smaller than previously possible with a torque magnetometer, as well as the various loop properties previously not obtainable with a torque magnetometer. All sections of the film are sensed uniformly in marked contrast to coil sensing devices. Unlike the usual ac B‐H hysteresigraph, the torque B‐H hysteresigraph is not affected by eddy currents in metal substrates.