We have determined the blocking temperature distribution Tb(T) in spin-valve sheet films with FeMn, IrMn, PtMn, NiMn and CrPdMn antiferromagnetic layers (AFM). We find a clear dependence of Tb(T) on the field applied during the measurement, which we link to the reversal state of the pinned layer through the torque applied on the AFM. Using fields large enough to fully reverse the pinned layer, NiMn and PtMn show little or no components of the blocking temperature below 150 °C, whereas both IrMn and CrPdMn (the latter in a “synthetic” AFM design) exhibit important low-temperature trailing edges of the distribution. Accelerated annealing experiments in a low reversed field equivalent to the self-demagnetizing field in a micron-size head allows us to access the time to failure and the failure activation energy from which the expected lifetime can be assessed. We find a general correlation between the expected lifetime and the fraction of loose (e.g., unblocked) AFM spins at any given temperature. Accordingly, only NiMn and PtMn are found to exhibit a sufficient long-term stability for disk-drive operations.

No abstract

No abstract

The blocking temperature distribution Tb(T) and the failure activation energy (as defined by a 10% drop in the magnetoresistance amplitude in a reverse field equivalent to the self-demagnetizing field of a micron size stripe height device) have been determined in spin-valve sheet films with FeMn, IrMn, PtMn, NiMn, and CrPdMn antiferromagnetic exchange biasing layers. We find a clear correlation between the expected lifetime and the fraction of loose (e.g., unblocked) antiferromagnetic grains, which we believe is due to pinned layer rotation being the main failure mechanism in these systems. For CrPdMn structures, a good agreement is found between the stability of sheet films and of finished sliders. From these data, only NiMn and PtMn appear to be suitable for disk-drive applications.