Thermal variations in switching fields for sub-micron MRAM cells

Thermal effects in switching of sub-micron tunnel junctions are investigated. The switching field is shown to he inversely dependent on temperature, and switching field jitter is shown to be strong function of temperature. Micromagnetic modeling is used to understand thermal effects. In some instances a stability factor (defined as KV/kT) of 100 or more may be required for acceptable switching field jitter, while with proper optimization of FM layers, stability factors of 50 or 60 may suffice.