Peter Andreas Grünberg
1939–2018, Plzeň, Czechoslovakia, Jülich, Germany
German physicist who co-discovered giant magnetoresistance (GMR) in the Fe/Cr/Fe trilayer in 1988 — foundation of modern hard-drive read heads.
Grünberg earned his PhD at the Technical University of Darmstadt in 1969, did postdoctoral work in Ottawa (Carleton), then joined Forschungszentrum Jülich in 1972, where he studied thin-film magnetism for life.
He discovered two key phenomena: antiferromagnetic coupling of two iron layers across a thin chromium spacer (1986), and giant magnetoresistance in the Fe/Cr/Fe trilayer (1988), independently and simultaneously with Fert's group. He early recognized its application potential and filed a patent in 1988. He shared the 2007 Nobel with Albert Fert.
Nobel-winning work
At Jülich, Grünberg studied ultrathin iron layers separated by non-magnetic spacers. In 1986 he proved that two iron layers could couple 'antiferromagnetically' across a few atomic layers of chromium — one layer always opposing the other. Applying an external field to force them parallel, he measured a pronounced resistance change: giant magnetoresistance, published 1988 alongside Fert's.
Unlike Fert's GMR in multilayers (needing large fields), Grünberg's trilayer is the direct ancestor of the 'spin valve' — the structure that made ultra-sensitive read heads possible. This blend of fundamental discovery (thickness-dependent spin coupling) and technological invention is why the 2007 Nobel went to both men.
Workplaces: Forschungszentrum Jülich
Germany