Magnetic thin films for spin-transfer torque applications

Abstract

Current-induced magnetisation reversal of a nanomagnet by spin-transfer torque (STT) is of great technological importance owing to the scalability of the switching mechanism. An application of the STT phenomenon is the spin-transfer torque magnetic random access memory (STT-MRAM), where the basic building block of the memory is a magnetic tunnel junction (MTJ). STT-MRAM has shown promise as a candidate for next-generation non-volatile memory because it combines fast access time, high endurance, high scalability and ease of integration into the CMOS process. However, a main challenge of the technology is to reduce the uncomfortably high switching current density jc > 1 x 10'10 A m-2 which has to be applied perpendicularly to an MTJ device, across the ultrathin insulating tunnel barrier, in order to write the information. The high jc increases the risk of dielectric breakdown and leads to higher power consumption as well as Joule heating. In this thesis, the issue of high jc is addressed via three different strategies ...