MOKE study of Co/Ti/(Gd–Co) multilayers near the magnetic compensation state

The magnetic behaviour of [Co/Ti/a-Gd0.36Co0.64/Ti]4/Co layered structures was studied by means of the transversal magneto-optic Kerr effect, with Ti spacers of different thicknesses. Within the Gd0.36Co0.64 amorphous layer, the Gd magnetic sub-lattice dominates at all investigated temperatures. The strong exchange interaction at the interfaces causes ‘macroscopic ferrimagnetic behaviour’ in the whole system. The existence of a magnetic compensation state in the complete multilayer system was manifested by the change of sign in the magneto-optic hysteresis loops and the increase of coercivity. The evolution of the critical field for a spin-orientation transition leading to a non-collinear magnetic state near the ‘compensation temperature’ can be described within molecular field theory. The influence of the non-magnetic spacer thickness on the characteristics of the compensation state is also discussed.