Critical dimension of the transition from single switching to an exchange spring process in hard/soft exchange-coupled bilayers - art. no. 184403

Hard/soft exchange-coupled Ni80Fe20/Sm40Fe60 bilayers with well-defined ind uced in-plane uniaxial anisotropy were deposited on (100) Si and glass subs trates by dc magnetron sputtering. The magnetization-reversal process was s ystematically studied by analyzing the magnetic hysteresis loops measured b y the alternating-gradient magnetometer and surface-sensitive magneto-optic Kerr effect. The coercivity in the single-switching process and the nuclea tion field in the exchange spring process are quantitatively described by t heoretical models. As a result, a critical dimension equation describing th e transition from a single-switching, process to an exchange spring process is developed. Different magnetization-reversal processes are essentially d etermined by the exchange length (or domain wall width) of the soft layer u nder an external field and the pinning energy exerted on the domain wall of the hard layer near the interface.