Tuneable exchange-spring stiffness in amorphous magnetic trilayer structures.

We investigate the magnetic properties of amorphous Sm10Co90/Co60(Al70Zr30)40/Co85(Al70Zr30)15exchange-spring magnet trilayers. The magnetically soft Co85(Al70Zr30)15layer is coupled to the magnetically hard Sm10Co90layer through the weakly magnetic low-TcCo60(Al70Zr30)40spacer layer. The strength of the coupling can be controlled with temperature and the coupling persists above the intrinsicTcof the spacer layer due to a long-range magnetic proximity effect. Polarized neutron reflectivity is used to examine the magnetic profile of the trilayers during magnetization reversal. A two-step switching occurs, with the switching angle of the soft layer strongly dependent on the strength of the coupling. In the strong coupling regime a magnetic state can be achieved where the soft layer magnetization is perpendicular to the hard layer whereas in the weak coupling regime the soft layer reverses fully.