Nonlinear temperature dependent nucleation field in perpendicular exchange spring typed magnetic tunnel junctions

The nonlinear temperature dependence of nucleation field (Hn) of [Co/Pt]n multilayer based perpendicular magnetic tunnel junction stacks with wedged Co60Fe20B20 insertion layers is reported. When temperature decreases, the tilted spins away from perpendicular direction near Co60Fe20B20/AlOx interface play dominating role to promote the nucleation process and lower Hn value and even change the sign of Hn. By taking advantage of high temperature annealing under high perpendicular magnetic field, this nonlinear behavior and sign of Hn could be manipulated. The understanding of temperature dependent properties in such system is important for spintronics applications, such as in memory and spin oscillators.