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Albert Fert and the LPS

With the courtesy of Gaelle Degrez from Plein Sud magazine of the Université Paris-sud (nbr 69, january-february 2008) we recall below the link between Albert Fert and the Laboratoire de physique des solides. This article is based on interviews. Moreover, reprints of some representative papers from this period are available at page 3 of this article.


On the 10th December 2007, Albert Fert received from the King of Sweden the medal and diplomas of the Physics Nobel Prize for work on the giant magneto-resistance that has paved the way to a new form of electronics, called spintronics. In order to give the story of the background to this triumph, we have interviewed two people who played an important part in the events leading up to it : Jacques Friedel, the founder of the Laboratoire de Physique des Solides (Solid state physics laboratory in Orsay) who is famous for his work on the theory of metals, and Ian Campbell, a CNRS research director, who was the Ph.D supervisor of Albert Fert.


Where does the physics of spintronics come from and when was it discovered ? The first date which comes to mind is 1988, the year where the founding paper by Albert Fert and his collaborators was published in Physical Review Letters. But as every discovery is the outcome of something that was started years before … we should begin by going back in time.


When the physicists of the Sorbonne moved to Orsay


Our first stop will be in 1959. Why that year ? Because it was in 1959 that André Guinier, Raimond Castaing and Jacques Friedel founded the Laboratoire de physique des solides (LPS) on the Orsay campus. “We had no square meters at the Sorbonne” remembers Jacques Friedel, “Mr. Guinier had a small cupboard at the Arts et Métiers, I had my office at the Ecole des Mines and Castaing had nothing as he was coming from Toulouse. We went to see Yves Rocard who was then Director of the Physics department of Ecole Normale Supérieure and in charge of building the great particle accelerator on the Orsay campus. Yves Rocard had some supplementary budget to be used to construct a building for the high energy physics theoreticians. We explained our situation. He thought over it for five minutes and then proposed to add a wing to the rectangular building that was planned.” These three physicists had known each other for quite some time and had every reason to want to work together. André Guinier and Jacques Friedel had created together a Master course on Solid state physics. Both worked on metals, with André Guinier looking especially at the atomic structure whereas Jacques Friedel focused on the electronic structure. Raimond Castaing was an experimentalist ; he was the first Ph.D student of André Guinier. It was he who developed the Castaing probe (EPMA), a method for measuring the atomic composition of alloys by bombarding them with electrons which excite the atoms in the alloy. The team, soon joined by Pierre-Gilles de Gennes (Nobel prize in Physics in 1991) settled first in the new wing of the building #210. They were to stay there until 1970, when the LPS moved to a new building #510 that was specially built for it on the Plateau du Moulon, where the laboratory still stands.


André Guinier (left) and Jacques Friedel (right)


Solid state physics in France after the War


At the beginning of the sixties, Jacques Friedel was one of the pioneers of the study of the electronic structure in metals and alloys. This is of paramount importance when one knows that the characteristics of electrons in metals underlie the mechanical and electronic properties of metals and alloys as well as their magnetic properties. These properties depend on complex effects linked to the interactions between electrons and to the presence of impurities with electric charges. Jacques Friedel played a central role in the understanding of these phenomena. He is a theoretician and wanted, as did Pierre-Gilles de Gennes, to be surrounded by young experimentalists in Solid state physics, specialists of metals. This was not that easy in post-war France, where the efforts in Physics were mainly devoted to to semiconductors. Few laboratories were concerned with metals (with the important exception of the laboratory of Louis Néel in Grenoble, devoted largely to Magnetism). So, Jacques Friedel recruited three young researchers : J.P. Burger from the Laboratoire de magnétisme in Strasbourg, C. Froidevaux, a Swiss from the Polytechnicum in Zürich, who had specialized in resonance techniques at Berkeley after a Ph.D with Nicholas Kurti in Oxford, and finally Ian Campbell who also had done an experimental Ph.D with N. Kurti in Oxford on nuclear techniques at low temperatures. Ian Campbell, who is going to play a major role in our story, arrived at the LPS in 1964. He had obtained a fellowship from the Royal Society in order to stay for a post-doc in the Laboratoire de Physique des Solides, with Jacques Friedel. “When Jacques Friedel came to ask me about what subject I wanted to study I proposed - among other themes – electronic transport in ferromagnets. It seemed to me that there was an interesting path to follow by confronting the ideas developed by the British physicist Nevill Mott as early as 1936 and the more recent ones from Jacques Friedel and his group about the electronic structure of alloys. Mott had proposed that the electronic conductivity in ferromagnets should be carried in parallel by spin up and spin down electrons, but nobody had ever tested this experimentally. Friedel agreed with that idea but I told him that I had neither apparatus nor sample nor team. He told me he would think it over ; we met again one month later. He had found a cryostat available on weekends in the superconductor team led by Pierre Pério. He had in addition received a letter from English colleagues who were proposing to pass on some samples that happened to be ferromagnetic alloys. And he added “and moreover, there is a normalien who is looking for a Ph.D subject, could he work with you ?” I did not know what a normalien was …”


We are now at the beginning of 1965. Ian Campbell met Albert Fert for the first time. He proposed him the Ph.D subject that Albert Fert was to to investigate, on the electronic transport properties of Nickel and Iron.