The hotspot and current self-heating effects on the spin-transfer-induced magnetization switching are investigated for low resistance magnetic tunnel junctions. Two kinds of spin torque theories, one for ohmic-like conduction from randomly distributed hotspots and the other for tunnel conduction from an insulator barrier, are combined together in this study by using a parallel resistor model. We find that the spin torque amplitude is locally enhanced in the hotspot region due to the large current density, which leads to a strong reduction of the current switching threshold (Jc), in a way that the enhanced spin torque induces the local magnetization near the hotspot switching first, and then drives the switching spreading through the whole free layer. The current self-heating effect is also studied; the free layer temperature increases only a few degrees at an applied current close to Jc ∼1× 107 A cm2, which results in a slight decrease in Jc for the low resistance junctions with hotspots.
Bibliographical noteFunding Information:
This work was supported by the National Natural Science Foundation of China (Grant Nos. 10604016, 60678008, 60490290, and 10374019), grants from Shanghai Pujiang Program (Grant Nos. 05PJ14016 and 05PJ14090), and Shanghai Commission of Science and Technology (Grant No. 06DJ14007). The simulation work was supported by Fudan National High Performance Computing Center.