Appl. Phys. Lett. 99, 152105 (2011)

Magnetoresistance and phase change are two rival approaches to non-volatile memory, and have been developed largely independently of one another. Now, Alexander Kolobov and colleagues at the Japanese National Institute of Advanced Industrial Science and Technology and the Japan Synchrotron Radiation Research Institute have identified a system in which the two effects are intimately linked.

Magnetic random access memory exemplifies the magnetoresistive approach, and consists of two ferromagnetic contacts separated by a tunnel barrier. A magnetic field manipulates the alignment of the contacts, which leads to high or low resistance states. Phase-change memories, on the other hand, typically achieve switching by using current-induced Joule heating to alter the bulk structure of a conductor.

Kolobov and colleagues focused on interfacial phase-change memories, in which a solid–solid phase transition occurs at the interfaces (rather than the bulk) of a layered structure. Although the structure they chose is made of non-magnetic materials, certain alloys of these materials are topological insulators, which have conductive surface states that are sensitive to a magnetic field.

The researchers found that a magnetic field applied to their memory shifted its switching voltage and current–voltage slope. It was also capable of changing the behaviour of the device, from a memory cell to a threshold switch that is not hysteretic. The observation of combined magnetoresistive and phase-change effects may lead to the development of memories that combine the benefits of each technology.