TIME DECAY OF REMANENT MAGNETIZATION, REMANENT COERCIVITY, AND READBACK SIGNAL OF ULTRA-THIN LONGITUDINAL COCR12TA2 CR THIN-FILM MEDIA/

The time decay of remanent magnetization, remanent coercivity, and rea dback signal of ultra-thin longitudinal CoCr12Ta2/Cr thin film media h ave been studied experimentally with a VSM and a recording spin-stand tester using a MR read head, The time decay rate of the remanent magne tization or magnetic viscosity S increases significantly with decreasi ng magnetic layer thickness, especially for a M(r)t of less than 0.5 m emu/cm(2) and it is found to be strongly related to the strength of th e magnetic interactions between grains. For such thin media (CoCrTa=6 nm) with a M(r)t = 0.36 memu/cm(2), the readback signal amplitude decr eases at a high decay rate of about 5 % per decade of time (sec) which is found to be essentially independent of the linear recording densit y from 2000 to 6000 fc/mm, To obtain CoCr12Ta2/Cr media with a time de cay rate of less than 10 % in 5 years, the value of the ratio of the a nisotropy energy barrier to the thermal energy (Kv/kT) should be great er than 80 which corresponds to a CoCrTa thickness of greater than abo ut 10 nm.