Time decay of magnetization in longitudinal CoCrTa/Cr high density thin film media

A systematic experimental study of the time decay of the magnetization (M-decay) in longitudinal CoCrTa/Cr high density thin film media with different thicknesses at various levels of in situ reverse magnetic field which simulates the demagnetization field in recorded bits is presented. Two series of thin film media with the thickness of magnetic layer ranging from 90 Angstrom to 1500 Angstrom were deposited by RF/DC magnetron sputtering. The magnetic properties and M-decay were measured at room temperature using a vibrating sample magnetometer and an alternating gradient force magnetometer. The emphasis was placed on the M-decay at various film thickness. It is found that the coefficient of magnetic viscosity is not a constant over 5 decades decay time,(sec.), the M-decay percentage exhibits a well pronounced peak at the reverse field value of the remanent coercivity, and the mechanism of M-decay is apparently different in thin and thick film recording media. The mechanisms of affecting the magnetic viscosities of thermally-induced time decay are explored.