Magnetisation processes and hysteresis in magnetic multilayers with strongly and weakly coupled magnetic sun-layers

Magnetic phase diagrams and hysteresis loops for multilayers consisting of 3 magnetic sub-layers separated by 2 paramagnetic spacers have been calculated. The corresponding thicknesses have been chosen so as to make the exchange couplings, across the first and second spacers, simultaneously strong and weak, respectively. The calculations have been made within a phenomenological model, including bilinear exchange, Zeeman energy, and anisotropy terms. In order to minimize the number of fitting parameters the exchange coupling has been deduced from the total energy calculations based on the one-band tight-binding model. In some cases, the hysteresis loops reveal characteristic nearly flat regions typical for exchange-biased spin-valves. Moreover, the magnetic diagrams show what are the mutual orientations of the magnetic sub-layer magnetisations like, which is crucial for magnetoresistance properties. In particular the configuration with the largest amount of antiparallel orientation is expected to be the most resistive one.