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This study examined the structural, magnetic, and transport properties of CoFeSiB films with various Co compositions. The main focus was on two samples, amorphous Co74Fe4Si14B8 and nanocrystalline Co78Fe2Si12B8 thin films. The results show that the amorphous film is a typical soft magnetic material, while the nanocrystalline film has a large saturation field. It is believed that in a nanocrystalline thin film, a large saturation field is caused by antiferromagnetic exchange at the boundary between the amorphous and nanocrystalline phases. [ABSTRACT FROM PUBLISHER]

The typical double-barrier magnetic tunnel junction (DMTJ) structure examined in this paper consists of a Ta 45/Ru9.5/IrMn 10/CoFe 7/AlOx/free layer/AlOx/CoFe 7/IrMn 10/Ru 60 (nm). The free layer consists of an Ni16 Fe62 Si8 B14 7 nm, Co90 Fe10 (fcc) 7 nm, or CoFe t1/NiFeSiB t2/CoFe t1 layer in which the thicknesses t1 and t2 are varied. The DMTJ with an NiFeSiB-free layer had a tunneling magnetoresistance (TMR) of 28%, an area-resistance product (RA) of 86 Ω 11 μm², a coercivity (Hc) of 11 Oe, and an interlayer coupling field (Hi) of 20 Oe. To improve the TMR ratio and RA, a DMTJ comprising an amorphous NiFeSiB layer that could partially substitute for the CoFe free layer was investigated. This hybrid DMTJ had a TMR of 30%, an RA of 68 k Ωμ m², and a Hc of 11 Oe, but an increased Hi of 37 Oe. We confirmed by atomic force microscopy and transmission electron microscopy that Hi increased as the thickness of NiFeSiB decreased. When the amorphous NiFeSiB layer was thick, it was effective in retarding the columnar growth which usually induces a wavy interface. However, if the NiFeSiB layer was thin, the roughness was increased and Hi became large because of the magnetostatic Néel coupling. [ABSTRACT FROM AUTHOR]