Dynamic Heating in Micron- and Submicron-Patterned TbFe Films

The dynamic heating of micron- and submicron-patterned TbFe films using current pulses for the thermally assisted writing scheme has been investigated. The evolution of the required power/energy density with pulse width has been studied using experimental measurements and numerical thermal simulations. Two heating regimes (adiabatic and diffusive regimes) are revealed by simulation in the investigated range of the current pulse widths (0.01 ns–1 µs). The energy density required for writing is almost independent of the pulse width and element size, and about 13 pJ/µm 2 at the very short pulse width associated with the adiabatic regime. Two distinct zones are also observed in the diffusion regime, and the dependence of the heating power density on the pulse width variation (Δ t ) shows a 1-exp (-Δ t / t 1 ) phenomenological variation in each zone. The power/energy densities required for the writing of four patterned TbFe films with different sizes are measured in the range of the pulse width from 10 up to 1000 ns, and the experimental results are well explained by the simulation. The required power density for the writing of 0.74 µm 2 patterned films using the pulse duration of 10 ns is experimentally estimated to be around P = 2 mW/µm 2 , which corresponds to the energy density of E = 20 pJ/µm 2 .