  At the very heart of the successful phenomenological model of magnetic
hysteresis there is the so called Preisach distribution. In the existing
literature it is implicitly assumed, that this distribution has a mirror
symmetry. We show, by simple and convincing example, that this common
assumption is plainly wrong. Dropping it, we gain the ability to model not only
the usual hysteresis loops (major and minor) more accurately than ever before,
but also those displaying the exchange bias effect, what is impossible within
the framework of the symmetrical Preisach model. It is hoped, that our
observation paves the way towards the unified description of all the hysteretic
systems, including, but not necessarily limited to, superconductors,
(multi)layered structures, nanocrystalline materials, patterned media, and -
perhaps - the other non-magnetic hysteretic phenomena.

Materials Science