CoCrPt alloy thin film is one of the most promising candidates for ultrahigh density magnetic recording media. One of interesting issues for an application of ferromagnetic thin film to high density magnetic recording media is to investigate growth stress, since stress inevitably generated during thin film fabrication drastically alters magnetic properties as well as mechanical properties due to film fracture and buckling [1]. However, sufficient studies have not been addressed on in situ experimental investigation on stress evolution during film growth of magnetic thin film and its correlation with directly observed film growth structure. We have investigated in situ stress evolution of 400-Å (Co2Cr1){sub 100-x}Pt(subscript x)/1100-Å Ti alloy films with varying Pt concentration by means of an ultrahigh vacuum (UHV) chamber equipped with a highly sensitive optical deflection-detecting system [2]. Interestingly enough, the stress evolution patterns during the film deposition are remarkably changed with varying the Pt concentration. CoCrPt alloy films with lower Pt concentration (6 (less-than or equal to) x (less-than or equal to) 13) grow through compressive, tensile, and again compressive stress during film deposition, while CoCrPt alloy films with higher Pt concentration (21 (less-than or equal to) x (less-than or equal to) 28) develop with compressive and relaxed compressive stress without tensile stress generation. In situ stress-evolution behavior for 400-Å (Co82Cr18){sub 100-x}Pt(subscript x)/1100-Å Ti alloy films with the Pt concentrations of (a) 6, (b) 13, (c) 21, and (d) 28 at.% are demonstrated in Fig. 1. Here, the positive slope corresponds to tensile stress, while the negative slope implies compressive stress. The microstructural studies at the stress transition region reveal that film growth structure plays a major role in considerable change of stress evolution pattern in CoCrPt alloy films with the increase of Pt concentration.

In addition to grain size and distribution, compositional segregation of non-magnetic materials was also studied. A series of CoCrPtTa, CoCrPtB 5, and CoCrPtB8 thin film longitudinal media were prepared under ostensibly identical sputtering conditions. High resolution TEM revealed that adding 5% or 8% boron to the magnetic layer resulted in significantly reduced average grain size compared to the media with a CoCrPtTa magnetic layer. It was also found that by adding boron, SNR and media noise properties were improved. While not affecting the lattice mismatch between the underlayer and the magnetic layer, the presence of B was found to enhance Cr segregation to cores as well as grain boundaries.

Granular CoPt/C and FePt/C films, consisting of nanoparticles of the highly anisotropic fct CoPt (FePt) phase embedded in a carbon matrix, were made by co-sputtering from pure Co50Pt50 (Fe50Pt50) and C targets using a tandem deposition mode. The as-made films showed a disordered face centered cubic (fcc) structure, which was magnetically soft and had low coercivity. Magnetic hardening occurred after heat treatment at elevated temperatures, which led to increase in coercivity with values up to 15 kOe. The hardening originated from the transformation of the fcc phase to a highly anisotropic face centered tetragonal phase (fct) with anisotropy K> 10(exp 7) erg/cu cm. Transmission electron microscopy studies showed FePt particles embedded in C matrix with a particle size increasing from below 5 nm in the as-made state to 15 nm in the fully annealed state. These results are very promising and make these materials potential candidates for high-density magnetic recording.

Application-oriented book on magnetic recording, focussing on the underlying physical mechanisms that play crucial roles in medium and transducer development for high areal density disk drives.