Irreversible susceptibility of initial magnetization curve
  A method for estimation of reversible and irreversible susceptibilities of initial magnetization curves has been developed. It deals only with the energy necessary for magnetizing and demagnetizing the sample, not with the nature of the magnetization processes neither with a specific type of anisotropy, so it could be applied for a wide variety of real materials. A set of minor hysteresis loops of an initially demagnetized sample, plotted with progressively increasing maximum magnetic field, has been used. The obtained results showed an excellent coincidence with those calculated by the remanence curve method for a Stoner-Wohlfarth model system. 
G. Goev, V. Masheva, J. Geshev and M. Mikhov