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This paper reports on a systematic study of the effect of magnetic film thickness on the recording performance of perpendicular double-layered media. We found that the signal-to-noise ratio of the media decreases with increasing film thickness. This is mainly caused by the poorer head field gradient that results from the increased gap between the pole surface of the head and the top of the soft underlayer of the media. A theoretical study confirms the experimental findings. Index Terms--Magnetic recording, perpendicular recording media, signal-to-noise ratio.

The long-term stability of a CoCrPt perpendicular storage media has been investigated by thermal aging at temperatures ranging from 95 to 280 °C during otherwise normal ambient conditions. The signal-to-noise ratio from magnetic force microscopy images has been extracted by the autocorrelation method and compared for the different aging conditions. During aging at elevated temperatures, the media stack undergoes some structural and crystallographic changes. It is found that the severity of the aging process is higher for low-density bit patterns due to the higher value of demagnetizing fields for large bits. A comparison to the thermal aging is done with a set of disks in which a deterioration of the magnetic bit pattern was induced by an external magnetic field. Two experiments, including fields with a single polarity as well as with a cycled polarity, mimic different magnetic situations for the disk. During the external field experiments, no structural or crystallographic changes occur in the media. The magnetic background noise of the disks is also analyzed. For aging in a magnetic field, it is found that below a certain threshold value, mostly low-density bit patterns are affected by the aging process. However, above the threshold value, both low and high-density bit patterns are affected. [ABSTRACT FROM AUTHOR]

We study the noise performance of amorphous FeCoB soft underlayers (SULs) with radial magnetic anisotropy. 200 nm thick FeCoB films are sputter deposited and optionally postannealed for 8 s at different annealing powers. The correlation of SUL read-back noise with the magnetic and structural properties is studied using spin stand testing, in-plane magneto-optical Kerr effect measurements, magnetic force microscopy, and x-ray diffraction. The effects of annealing to achieve low read-back noise are examined. It is found that as-prepared films show large dc noise associated with stripe domains due to stress-induced perpendicular anisotropy. Thermal annealing reduces the internal stress and the films become magnetically anisotropic in the radial direction. The SUL-induced dc noise drops to the electronic noise floor, dc noise is found to decrease with an increase in annealing power until the films start to crystallize. [ABSTRACT FROM AUTHOR]

Stacking faults (SFs) and fcc-phased grains are studied by electron diffraction in perpendicular media. Co-alloy compositions, such as CoCrPt, CoCrPtB, are compared on different underlayers and deposition conditions. It is found that CoCrPtB alloys tend to have greater amount of SFs and fcc grains than the CoCrPt alloy. Underlayers as well as low deposition rate and base pressure help to reduce the amount of SFs and fcc phase. [ABSTRACT FROM AUTHOR]