The impact of number of repeats N on the interlayer exchange in $$[\text {Fe/MgO}]_{N} $$ [ Fe/MgO ] N (001) superlattices

Abstract

Abstract The strength of the interlayer exchange coupling in [Fe/MgO] $$_N$$ N (001) superlattices with 2 ≤ N ≤ 10 depends on the number of bilayer repeats (N). The exchange coupling is antiferromagnetic for all the investigated thicknesses while being nine times larger in a sample with N = 4 as compared to N = 2. The sequence of the magnetic switching in two of the samples (N = 4, N = 8) is determined using polarized neutron reflectometry. The outermost layers are shown to respond at the lowest fields, consistent with having the weakest interlayer exchange coupling. The results are consistent with the existence of quantum well states defined by the thickness of the Fe and the MgO layers as well as the number of repeats (N) in [Fe/MgO] $$ _{N}$$ N (001)superlattices.