Mapping buried magnetism
Magnetic properties of materials underlie technologies from old-fashioned recording tape to modern hard drives, and scientists are constantly pushing to develop new uses from magnetic behavior. Recently, researchers at MIT figured out how to use light pulses to map the magnetic direction and strength of a buried interface between two exotic materials, bismuth selenide and europium sulfide. In a sandwich of extremely thin layers of these materials, one distinguished by electrical conduction only on it surface, the other by becoming magnetic at extremely low temperatures, Nuh Gedik, the Lawrence C. (1944) and Sarah W. Biedenharn Career Development Associate Professor of Physics, and graduate student Changmin Lee measured the magnetism at the interface of the two materials. Their technique relies on a transformation that occurs at low temperature under an applied magnetic field as intense red laser light pulses pass through the sample and a small fraction of red light photons fuse together...