Thermal stability of high anisotropy cobalt based perpendicular magnetic thin films.

摘要

Perpendicular magnetic recording has long been considered a way to increase the areal density in magnetic materials over traditional longitudinal recording methods. Regardless of which recording scheme used, the thermal stability of magnetic media becomes increasingly important as the areal density of magnetic recording media increases. This dissertation is a study of the thermal stability of various perpendicular media. TbFeCo media, normally associated with magneto-optics, with perpendicular anisotropy and high squareness was found to have non-logarithmic decay curves that fit the Fatuzzo nucleation model. Studies of the magnetic viscosity at zero applied field for granular and multilayer cobalt based films were made to examine interparticle interactions. The effect of the demagnetization factor on the switching field distribution was found for two CoPtCr based granular films based on a log-normal distribution model. The linearity of the switching energy barrier as a function of applied field has been demonstrated for Co/Pd multilayers with non-coherent rotation. The effect of temperature on the thermal stability factor KuV/kBT has been measured for materials with high perpendicular anisotropy using both dynamic remanent coercivity and coercivity versus sweep rate methods. The results of these measurements are analyzed and compared to the known magnetic properties of bulk cobalt to draw some conclusions about the switching volumes associated with the materials and the physical meaning of the measurements.