Magnetic transition in Co/(Gd-Co) multilayers

[Co/Gd0.36Co0.64]4/Co multilayers with Co termination layer have been prepared by rf sputtering. They form macroscopic ferrimagnets with a compensation temperature (Tcomp) determined by the thickness ratio of the layers. In low fields the magnetization of Co and Gd-Co layers are along the axis of the applied field. Increasing field makes the moments of both the Co and Gd-Co layers deviate from the axis of the field giving rise to a transition into a twisted state. These magnetic transitions were studied by vibrating sample magnetometer (VSM), magneto-optic Kerr effect and magnetoresistance measurements at various temperatures. The nucleation and evolution of surface- and bulk-twisted magnetic states were also observed in these multilayers.