Soft magnetic properties and microstructure of NiFe(Cr)/FeCo/NiFe(Cr) films with large saturation magnetization

The soft magnetic properties of FeCo films, sandwiched by thin NiFe or NiFeCr films, are discussed in relation to the microstructure. Ta/NiFe(Cr)(5 nm)/FeCo(100 nm)/ NiFe(Cr)(5 nm)/Ta films prepared using the UHV sputtering process with pure Ar plasma show bcc-[110] preferred grain orientation of the FeCo layer with the [110] direction sharply perpendicular to the film plane, resulting in soft magnetic properties. No significant difference in soft magnetic properties was observed by the use of nonmagnetic NiFeCr layers instead of the NiFe layers, moreover, by varying FeCo composition between 25 and 30 at%Co. The best thickness of the FeCo layer in order to realize soft magnetic properties was found to be ∼100 nm in the present study, with a high saturation magnetization of 2.3 T. An addition of N₂ gas to Ar plasma during film deposition did not lead to an improvement of the soft magnetic properties. A film of [FeCo(100 nm)/NiFe(5 nm)]₄ layer structure was subjected to the fabrication of a single-pole-type recording head, and it is successfully demonstrated that the film has a sufficient softness to be used for the recording head application.