A magnetic tunnel junction (MTJ) structure with a composite free layer consisting of a nanocurrent-channel (NCC) layer sandwiched by two CoFe layers was proposed and investigated. The NCC layer increased the local spin current density inside the free layer and thus enhanced the writing capability for MTJ devices. In comparison with the conventional MTJ design with a single free layer, the intrinsic critical switching current density was reduced from 2.4× 107 to 8.5× 106 A cm2 by using the composite free layer. On the other hand, the thermal stability factor of the composite free layer, Ku V kB T, is around 149, which is almost the same as the value (159) for the MTJ device with a single free layer. The MTJ structure with the composite free layer is a candidate to solve the scaling problem for high density magnetic random access memory.
Bibliographical noteFunding Information:
This work was supported in part by the MRSEC Program of the National Science Foundation under Award No. DMR-0212302. The author would also like to acknowledge the Grant-in-Aid fund from Graduate School at University of Minnesota and partial support from Heraeus Mtd.
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