Reduction of Néel coupling in magnetic tunnel junctions containing an artificial ferrimagnet in the free layer

Magnetic tunnel junctions containing an artificial ferrimagnet (AFi) in the free layer are investigated. A lower offset field for the free layer is found compared to tunnel junctions with a single free layer of equal net magnetic moment. A reduction in Neel coupling up to 36% is achieved. The Neel coupling is interpreted in terms of the roughness parameters of the tunnel barrier. The combination of an AFi in the free layer with a robust exchange-biased hard layer, including an artificial antiferromagnet, leads to even lower values for the offset field. The sign of the offset field depends on the order of the layers inside the (free) AFi. The coupling strength of the AFi is further investigated in terms of layer thicknesses.