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Thermal-assisted switching, or TAS, is one of the new second-generation approaches to magnetoresistive random-access memory (MRAM) currently being developed. A few different designs have been proposed, but all rely on the idea of reducing the required switching fields by heating. The first design's cell, which was proposed by James M. Daughton and co-workers, had a heating element, an MRAM bit, an orthogonal digit line, and used a low-Curie point ferromagnetic material as the storage layer. In a second and more-promising design, which was developed by the Spintec Laboratory (France) and subsequently licensed to Crocus Technology, the storage layer is made of a ferromagnetic and an antiferromagnetic layer. When the cell is heated by flowing a heating current through the junction and the temperature exceeds the "blocking temperature" (Tb), the ferromagnetic layer is freed, and the data is written by application of a magnetic field while cooling down. When idle, the cell's temperature is below the blocking temperature and much more stable.
This approach offers multiple advantages over previous MRAM technologies:
- Because the write selection is temperature-driven, it eliminates write-selectivity problems;
- It is a low-power approach as only one magnetic field is required to write, and because the cell stability and magnetic susceptibility are decoupled as a result of the introduction of the blocking temperature; and
- It is thermally stable due to the exchange bias of the storage layer.
- Sousa RC, Prejbeanu IL (12 October 2005). Non-volatile magnetic random access memories (MRAM) (PDF). Crocus Technology. Retrieved 2012-12-23.
- Prejbeanu IL, Kerekes M, Sousa RC, Sibuet H, Redon O, Dieny B, Nozières JP (n.d.). Thermally assisted MRAM (PDF). Crocus Technology. Retrieved 2012-12-23.
- Hoberman, Barry (n.d.). The Emergence of Practical MRAM (PDF). Crocus Technology. Retrieved 2012-12-23.