Rotational hysteresis losses in isotropic media

A simple method of measuring magnetic rotational hysteresis losses in isotropic media is described. The method involves measuring the angular deceleration of a sample set rotating in a magnetic field. By using air bearings to minimise friction and allowing the moment of inertia of the rotating system to be varied, a maximum sensitivity of 10/sup -6/ J cycle/sup -1/ has been achieved with a precision of 3/spl times/10/sup -7/ cycle/sup -1/. The method has been used to measure rotational hysteresis losses as a function of applied field strength in isotropic samples of /spl gamma/-Fe/sub 2/O/sub 3/, AlNiCo and MQ1, a high coercivity NdFeB permanent magnet alloy. The data from these measurements was found to be in good agreement with that obtained by established methods of measurement.