Iron doping influence on interlayer magnetic coupling and magnetoresistance in Co/MoFe/Co films

Abstract

Abstract The interlayer exchange coupling and magnetotransport properties have been investigated in trilayer structures where two coupled symmetric Co layers were separated by a spacer. The trilayers have the following general structure: Co(dCo)/X(dspacer)/Co(dCo), where X stands for used spacer (pure Mo or codeposition Mo and Fe with chemical composition Mo0.8Fe0.2), dCo and dspacer are the thicknesses of the cobalt and spacer layers. Two samples sets were fabricated by molecular beam epitaxy: (i) wedge-like: the both Co wedges are similar (0–3 nm) and directed along one the side of the substrate while the spacer wedge (also 0–3 nm) was grown along perpendicular direction; (ii) uniform in thickness Co(3 nm)/X(0.7 nm)/Co(3 nm), exhibiting in-plane magnetization configuration and the strongest antiferromagnetic coupling. Magnetization processes were investigated using polar and longitudinal magneto-optical Kerr effect (MOKE) for studies of out-of-plane and in-plane magnetization configurations, respectively. With increase of dMo, the interlayer exchange coupling alternates between ferromagnetic and antiferromagnetic exhibiting as high as 0.3 T coupling field HIEC of antiparallel alignment for dMo = 0.7 nm. Iron doping results in about 3.5 times decrease of the HIEC, measured at first antiferromagnetic coupling range for both perpendicular and in-plane magnetization configurations. The oscillating dependence of HIEC on dspacer is analyzed in the frame of a Ruderman–Kittel–Kasuya–Yosida model. The giant magnetoresistance (GMR) effect has been investigated in the current in plane geometry. Relation between MOKE and GMR results is discussed.