Microstructures and properties of high saturation soft magnetic materials for advanced recording heads

This paper presents recent development on sputtered FeXN-based (X=Ta, Rh, Mo, Al, etc.) high saturation materials [1,2] and compare them with amorphous CoZr-based materials and electroplated NiFe- and CoFe-based materials [3,4] in the context of advanced high density magnetic recording. In particular, correlations among processing, microstructure and magnetic properties under oblique incidence and in laminated structures are discussed. Due to the extrinsic nature of coercivity, the mechanisms of soft magnetism are very complex and difficult to characterize. With the help of synchrotron radiation, pole figure analysis, transmission electron microscopy (TEM), torque magnetometry, and magnetic force microscopy (MFM), we can identify that (110) fiber texture plays a key role in the soft magnetism of FeXN films, in addition to the effects of film composition, stress, grain size and shape, and lattice spacing [5]. Soft films, both single and laminated, usually display well defined bcc (110) textures even on sloping surfaces. In contrast, films with poor (110) textures and asymmetric pole figures tend to have relatively large coercivities, and in certain cases possess perpendicular anisotropy and stripe domains. Processing conditions promoting (110) texture, including substrate bias, lamination with AlN, and appropriate base layer, lead to soft magnetism in FeXN films [6]. The addition of N and a third element, and lamination with insulating layers, result in significant increases in electrical resistivity, important to high frequency applications. The addition of N and X can also lead to enhanced pitting corrosion resistance [7].