Nanoscale magnet tests the Landauer limit

IEEE Spectrum : In 1961 Rolf Landauer of IBM theorized that there is a minimum amount of energy required by computational systems to reset or erase a bit of information. His calculations showed that at room temperature, that limit is 3 × 10⁻²¹ J (3 zJ). In 2012 a team of researchers demonstrated that the limit could be reached in a nonmagnetic physical system. Now Jeffrey Bokor of the University of California, Berkeley, and his colleagues have shown that Landauer’s principle does apply to a magnetic system more representative of actual computer storage. Bokor’s team created an array of nano-sized magnetic dots that were magnetically aligned. Using an external magnetic field, the scientists could flip the dots between binary states and effectively erase the data that the dots stored. The team found that the dots consumed around 6 zJ of energy at room temperature—twice the Landauer limit but within the level of uncertainty of the experiment. The researchers suggest that slight variations in the orientations of the magnets were enough to account for the higher value.