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

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.