A Boost for Superconducting Logic

The key component of state-of-the-art magnetic memories and sensors is a device called a spin valve, whose electrical resistance depends on the relative alignment of the magnetizations of two thin ferromagnetic elements. Researchers are interested in developing superconducting analogs of the spin valve to be used in “cryogenic memory” technologies that consume little power and dissipate little heat. In this case, changing the relative alignment of the two ferromagnets shifts the transition temperature T_c of an adjacent thin superconducting layer—an effect that can be used to turn the superconducting state on (or off) and lower (or raise) the device’s total resistance. But so far, the T_c shifts observed in experiments have been too small for practical use. Jan Aarts and his colleagues at Leiden University in the Netherlands demonstrate superconducting spin valves in which T_c changes by nearly 1K[1], an order of magnitude increase compared to previous schemes.