Magnetic relaxation at high linear densities in thin films with perpendicular magnetic anisotropy

Abstract

We have measured the rate at which recorded signals decay in perpendicular Co78Cr17Ta5 alloys, Co70Cr15Ta5Pt10 alloys, and Pd/Co multilayers. At low write frequencies, the magnetization decay resembles that observed by magnetometry. At high write frequencies, the relative decay rate decreases substantially. This is attributed to a change in the demagnetizing energy associated with high linear densities in perpendicular media. A model for magnetization decay is used to deduce the activation volume, the size distribution, and the barrier to flux reversal which exists for the alloy films. A time scale tε is introduced, over which the decay rate is dominated by the initial condition applied by the write head. The observed decay in the multilayers was much lower (<0.5%/time decade) than in the alloys (3%–4%/time decade) at all of the spatial frequencies tested.

Magnetization Decay in CoCr-alloy Perpendicular Magnetic Recording Media

“…7, the magnetic layer thickness of less than 17 nm may be too small to keep the recorded bits stable against the thermal fluctuation. Small magnetization decays have been reported for the PdlCo multilayer perpendicular media [12]. As shown above, similar small decay characteristics are achievable by using the single-layer CoCr-alloy films with Mr/Ms > 0.95.…”

Disk drive integration issues for perpendicular recording

“…These include fundamental issues such as thermal relaxation of perpendicular media [3], [4], underlayer effects, and narrow erase bands [2], as well as integration issues such as head skew, changes in signal decoding, and servo compatibility. A number of the fundamental issues have been addressed in the recent Hitachi demonstration of 52 Gbits/in [4], as well as theoretical considerations for perpendicular recording [5].…”

Thermal Stability of Perpendicular and Longitudinal Recorded Information

“…However, since the demagnetizing field is strong for low recording densities, thermal decay of magnetization occurs in perpendicular media [4][5][6][7]. We must not ignore the problem of thermal fluctuations at low densities in perpendicular recording media as long as the current sector servo method is used.…”