Most electronic gadgets function by moving around electric charges. The nascent technology of spintronics, however, makes use of not only the charge of electrons but also their spin. Spin is closely related to magnetism, and the first spintronic devices include read heads of computer disk drives and magnetic random-access memory (MRAM); the latter retains its data even when the power is off [see "Spintronics," by David D. Awschalom, Michael E. Flatté and Nitin Samarth; Scientific American, June 2002]. But spintronic computer chips and other more complex gear are not yet possible--unlike MRAMs and read heads, they might need magnetic semiconductors, and existing semiconductors are not magnetic at room temperature. Several groups have recently made significant progress in this direction.

One of the most studied magnetic semiconductors is gallium arsenide doped with manganese. In 1998 a group led by Hideo Ohno of Tohoku University demonstrated that this substance can remain ferromagnetic up to 110 kelvins (-163 degrees Celsius). (Ferromagnetism is the technical term for magnetism that persists after an applied field is turned off.) At liquid-nitrogen temperatures, this material has been used to demonstrate devices such as spintronic light-emitting diodes (LEDs), which emit light polarized according to the spin polarization of the electrons and holes that generate it.

This article was originally published with the title Getting Warmer.

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