L1 ₀-FePt based exchange coupled composite films with soft [Co/Ni] _N multilayers

Perpendicular exchange coupled composite structures were prepared, utilizing L1 ₀-FePt as the magnetic hard layer and [Co/Ni] _N multilayers as the soft layer. Sharp reduction of the switching field was observed with increasing periodic number N of [Co/Ni] _N multilayers. By inserting a thin Pt interlayer between L1 ₀-FePt and [Co/Ni] _N layers, it is found that in order to get the best of exchange coupled composites, different interlayer coupling stiffness was required in the composites with different soft layer thickness. Furthermore, the angular variation of the coercivity and remanent coercivity shows high angular tolerance to applied field angle, and reveals the evolution of magnetization reversal from incoherent rotational mode to dominant wall motion with increasing thickness of soft layer.