Thermomagnetic writing on deep submicron-patterned TbFe films by nanosecond current pulse

This work studies the heating process for deep submicron-patterned TbFe films to be used in a thermally assisted perpendicular magnetic random access memory's writing scheme. The dependence of the heating power density with the current pulse width required for the successful writing was measured in the investigated range of 5–100 ns. In the case of long current pulse, the heat diffuses dominantly into substrate, which resulted in large variation of the required power/energy density with the patterned size. The power/energy densities required for writing increased as the junction area is reduced. While for the short current pulse width, the power/energy densities became rather independent on the size. The required power density for writing 0.38×0.28 μm2 patterned films using the pulse width of 5 ns is experimentally estimated to be around P=4.7 mW/μm2, corresponding to the energy density of E=23 pJ/μm2, under an external field of 100 Oe.