Grünberg, Peter Andreas (pāˈtər ändrāˈäs grünbĕrkˈ) [key], 1939– German physicist, b. Pilsen, Germany (now Plzeň, Czech Republic). After receiving his Ph.D. at the Darmstadt Univ. of Technology in 1969, he was a postdoctoral fellow of the National Research Council of Canada at Carleton Univ. in Ottawa. Grünberg joined the Institute of Solid State Research at Research Centre Jülich in Germany in 1972, where he became a leader in the field of thin-film and multilayer magnetism. This led to his discovery in 1988 of giant magnetoresistance (GMR), so called because tiny changes in a magnetic field produce large changes in electrical resistance. For this discovery, which led to the development of spintronics, he shared the 2007 Nobel Prize in physics with Albert Fert, who had independently discovered the same effect.