Peter Grünberg, an inspiration for many magnetic ICMABers: from spinwaves to GMR
- News 06 August 2018 630 hits
"Peter Grünberg was one of the first physicists to understand the potential of nascent nanotechnologies for fundamental research. He discovered giant magnetoresistance, or GMR: a large change in electrical resistance induced by a small magnetic field in stacks of ultrathin magnetic and non-magnetic layers." says Albert Fert* in Peter Grünberg's Obituary in Nature.
Only 10 years!
"I believe that it is thanks to this discovery (for which Peter Grünberg and Albert Fert won the Nobel Prize in Physics in 2007) that we can continue working with magnetic materials with the vision of integrating them in our current technology. In fact, I think that this case is one of those rare cases, in which only after 10 years of the scientific discovery (which was published in 1988-1989), hard disks that used the tecnology based on it appeared. In only 10 years!" says Ferran Macià, ICMAB researcher working on spintronics and magnetic materials in the MULFOX group.
"Applications of this phenomenon (GMR) have revolutionized techniques for retrieving data from hard disks. The discovery also plays a major role in various magnetic sensors as well as for the development of a new generation of electronics. The use of Giant Magnetoresistance can be regarded as one of the frst major applications of nanotechnology." (cited in The Nobel Prize in Physics 2007)
Discovery by accident
From Fert's obituary "Grünberg quickly demonstrated his pioneering spirit, developing the spectroscopy technique of Brillouin light-scattering spectroscopy (BLS). BLS examines the inelastic scattering of light; it can probe both the ground state of magnetic materials and their excited states. In the 1970s, physicists were struggling to pick up the specific excitation modes expected to occur at the surface of magnetic materials. Grünberg singled out these modes, and identified them as spin waves of the Damon–Eshbach type", Josep Fontcuberta says: "This discovery, that was pivotal to understant shortly after the magnetic coupling between two magnetic layers separated by a metal and, lastly, the GMR, was by accident."
"Peter Grünberg and colleagues were working on BLS with EuO (Europium Oxide). A breakdown in the power supply of an electromagnet and the subsequent repair and reconnection led to observe a result that was opposed to what they had observed before the breakdown. After reviewing it, they realized that what they saw depended on how the power supply was connected, and therefore, the directon of the created magnetic field. This made them see the magnetic character of a certain absorbtion, which resulted to be a surface spinwave (the Damon Esbach, which Fert mentions). This was crucial for the subsequent experiments that allowed them to discover and understant the GMR"
Figure: Peter Grünberg and Albert Fert in 2007.
"Wise men are wise because they admit that progress has something to do with good luck."
Affirms Josep Fontcuberta, ICMAB researcher, leader of the MULFOX group and IEEE Magnetics Society Distinguished Lecturer 2016.
- Peter Grünberg (1939-2018) Obituary by Albert Fert (Nature, May 2018)
- The Nobel Prize in Physics 2007 - What is giant magnetoresistance?
- Peter Grünberg's Nobel Lecture - You will find a good explanation of the breakdown of the system that led to the discovery of Damon Esbach surface mode
*Albert Fert is a physicist at the University Paris-Sud in Orsay and at UMPh, a joint laboratory of CNRS and Company Thales. e-mail: firstname.lastname@example.org. Nobel Prize in Physics 2007, together with Peter Grünberg.