Materials Science

Thinning the Switch

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Science  02 Dec 2011:
Vol. 334, Issue 6060, pp. 1184
DOI: 10.1126/science.334.6060.1184-c
CREDIT: ISTOCKPHOTO.COM

Even though the name might not mean much to you, a magnetic tunnel junction (MTJ) is probably closer to you than you think, given that it's a standard component of hard disk drive read heads. MTJs consist of an oxide material sandwiched between two ferromagnetic (FM) layers, and their function depends on reliably manipulating the magnetization of these FM layers, usually by applying an external magnetic field; the induced switching between low- and high-resistance states corresponds to 1 or 0 bits. Using electrical currents for manipulation would be preferable, but the high current density required cancels the benefits. Now, Wang et al. have used electrical voltage to reversibly alter the magnetic properties of the junction, enabling much smaller currents to control the switching. The key modification is the use of very thin layers of Co40Fe40B20 as the FM (with the standard MgO as the oxide), which makes it possible to control the magnetic anisotropy, and thus the coercivity, with electric fields. The results are expected to pave the way toward ultralow-energy switching in MTJs, a major goal in the field.

Nat. Mater. 10.1038/nmat3171 (2011).

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