When laboratory researchers first tried to duplicate Freeman's simulations of a monolayer on a neutral surface, the experiments failed. "One of the crucial experiments for monolayer magnetism was iron on silver," says Freeman. "They did photoemission, looking at what happens to electrons emitted from the surface. They found no magnetism."
The researchers, it turned out, were looking in the wrong direction. In most cases, magnetic moments align parallel to the plane, but in this case, they align perpendicularly, vertical instead of horizontal. With corrected technique, the researchers found the magnetism. "In an attempt to confirm or refute the predictions of enhanced magnetism," Freeman says, "they discovered something very important for applications in magnetic recording."
The perpendicular alignment permits packing more information. This factor coupled with the stronger magnetic moment of a single-atom layer is transforming the magnetic recording industry of compact discs and lasers. Freeman, along with Wu and visiting professor Dingsheng Wang of the Academy of Sciences of China in Beijing, developed a new computational approach -- the state-tracking scheme -- that predicts which materials have magnetic moments oriented perpendicularly. Along with enhanced storage, the new magnetism revealed by Freeman's work broadens the choice of materials beyond conventional oxide discs.
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