Researchers at Ohio State in Columbus and at the University of Utah in Salt Lake City have demonstrated photo-induced magnetization in a plastic sample. The work, which they reported in the Feb. 4 issue of Physical Review Letters, could lead to the development of magneto-optical write heads in polymer-based computer hard drives.The team discovered that manganese-doped tetracyanoethylene becomes 1.5 times as magnetic when exposed to blue light for six hours at up to 75 K. The subsequent application of green light partially demagnetized the film, and thermal treatment reversed the effect.