Search

A study of the relationships between the microstructure and magnetic properties of cobalt alloy magnetic thin films and chromium underlayers deposited onto circumferentially textured NiP/Al substrates is presented. The variation of the chromium microstructure as a function of argon pressure and substrate temperature during sputtering is analyzed using high resolution scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM). This combination shows that the layers grow in columns which have increasing physical separation with increasing pressure and decreasing temperature. Crystallographic grain separation, however, follows a different trend because intercolumnar crystallographic alignment decreases with increasing temperature. TEM is also used to show how the growth of the chromium underlayer affects the cobalt alloy layer and to analyze the resulting microstructures in different magnetic alloy layers. The noise properties of the magnetic alloy are correlated with the observed size of the physically and crystallographically distinct units.

We have experimentally examined the micromagnetic structures in CoCrTa/Cr films deposited onto NiP/Al substrates at 25, 100, 150, 200 and 250 [degrees] C.We prepared all the films in an acerased magnetic state. The Lorentz transmission electron microscopy images demonstrate a monotonic decrease of magnetic cluster size with increase of deposition temperature and the magnetic force microscopy results show a decrease of image contrast. This indicates a decrease of intergranular exchange coupling with increase of deposition temperature. Nanoprobe energy dispersive spectroscopy (EDS) reveals an increase of Cr segregation at CoCrTa grain boundaries with increase of deposition temperature. The correlation of micromagnetic and microcompositional observations supports that Cr segregation at grain boundaries is responsible for decoupling CoCrTa grains. Our nanoprobe EDS results also indicate that the Cr diffuses to the grain boundaries from the inside of the CoCrTa grains as opposed to a diffusion process involving the Cr underlayer.

We have studied micromagnetic structures in real computer hard disks, with emphasis on magnetic vortices and ripples at bit-transition regions and track edges, using Lorentz transmission electron microscopy (LTEM). A combined dimpling and chemical etching method was used to produce LTEM specimens of Co alloy/Cr with large, uniformly thin areas from the typical C/Co alloy/Cr/NiP/Al(substrate) hard disk structures.

The effect of CoO addition on the magnetic, microstructure and recording properties of CoNiPt media is discussed. Both Hc and squareness increased with increasing CoO. This was attributed to the uniform grains of CoNiPt-CoO which were isolated by a channel of about 10-20 [Angstrom]. This results in an increase in SNR of about 6 dB for 2% of CoO. The OW of CoNiPt-CoO media was found to be higher than the CoNiPt media sputtered in presence of oxygen.

A quantitative MFM technique to determine the magnetic orientation in longitudinal media at the microscopic level is described. The remanent magnetization orientation ratio measured by this MFM technique correlates well with the orientation ratio measured using a VSM. The analysis used to determine the orientation ratio from MFM images is based on the disorder noise model. The experimental results show that orientation is reflected in medium noise and interaction effects, as measured using the delta M technique. Index Terms--Delta M, MFM, orientation ratio, VSM.