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Erwin-Félix Lewy-Bertaut, born on 9 February 1913 in Leobschütz (Poland, then Germany) and died on 6 November 2003 in Grenoble, France, was a French scientist renowned internationally for his work in the fields of neutron scattering and crystallography.

Born as Erwin Lewy in Silesia (then in Germany), he received a training as a lawyer. As his family was Jewish, when the Nazis came to power he left Germany for France, becoming a French citizen in 1936 and starting a scientific career as a chemical engineer. At the start of the Second World War, he joined the French army and, following the defeat of 1940, his military commander gave him the papers of a deceased soldier and a new identity: Félix Bertaut. His family, whom he had brought to Bordeaux, were arrested and disappeared into the camps in Germany. He then went to Paris and Grenoble to work with Louis Néel, where he learned about solid state chemistry and X-ray diffraction and became a crystallographer and a physicist of magnetism. He also became a pioneer in neutron diffraction and, with Louis Néel, played a leading role in the creation of the European research institute ILL (Institut Laue-Langevin). He was a man of great culture and the impact of his scientific studies meant that he held positions of responsibility in the main international crystallography and physics organisations. He was a member of the French Academy of Sciences.

From Erwin Lewy to Félix Bertaut (1913 - 1946)

Erwin Lewy was raised within the confines of a conventional Jewish household. The year 1930 marked a significant shift as his mother passed away, prompting their entire family's relocation to Gleiwitz amidst an era of economic turmoil and the ascent of Nazism. Following this, in 1931, Lewy embarked on his legal studies first in Freiburg and subsequently in Breslau (now Wrocław). As Hitler's ascendancy to power unfurled in Germany, instituting a "numerus clausus" that effectively precluded Jewish individuals from university access, Lewy, aged twenty at the time, encountered aggression from a faction of Hitler Youth.

This relentless environment of hostility, coupled with his perusal of Mein Kampf, instilled a profound comprehension of the gravity of the circumstance. Imbued with a deep affinity for French culture, Lewy contemplated migration to Paris. Ultimately, he charted a different course, finding himself in Bordeaux. There, the Rothschild Foundation bestowed upon him a scholarship, facilitating his enrollment at the university. In Bordeaux, Lewy not only achieved a degree in chemical engineering but also secured degrees in physics and mathematics. Noteworthy among his instructors was the eventual Nobel laureate, Alfred Kastler. To bolster his financial resources, Lewy undertook roles as a mathematics and German tutor. Among his pupils was the future academician Jean-Claude Pecker.

Erwin Lewy acquired French citizenship in 1936. In February 1939, fully aware of the peril of Nazism, he relocated his family to Talence, near Bordeaux. Just prior to the outbreak of World War II, he suspended his initial doctoral pursuit involving rosin to voluntarily join the French army. At the onset of the conflict in 1940, Colonel Faure entrusted him with the military records of a missing soldier, Félix Bertaut. This became his sole identification for an extended period, and in tribute to the anonymous Frenchman who allowed him to cloak his identity, he adopted this name permanently.

Employed as a chemical engineer in the unoccupied region in Barbaste, he focused on enhancing the durability of bicycle brakes crafted from agglomerated cork. This was crucial as bicycles stood as the predominant mode of transportation during that era. The French police in the free zone, under Vichy's directives, could not prevent the abduction of his family and his rabbi father from Bordeaux by the Nazis, leading to their internment in concentration camps. Not until 1978 did he learn of their deportation to Auschwitz via Drancy.

To elude police inspections and evade mandatory labor service, he found himself compelled to journey to Paris. There, Alfred Kastler recommended that he collaborate with Marcel Mathieu at the Central Laboratory for Powders (L.C.P.). Subsequently, he partnered with Emmanuel Grison, the future head of the Atomic Center of Saclay, who tutored him in the utilization of the International Tables for the Determination of Structures—an introduction to crystallography. Regrettably, a bicycle registration check by the police led to his summons to the Paris Prefecture. Adhering to Marcel Mathieu's counsel, he embarked on a train journey the next day, armed with a mission directive endorsed by the L.C.P.'s director, bound for Grenoble in the Italian-occupied zone. His purpose was to meet Louis Néel, the future Nobel laureate, who was temporarily withdrawn from the University of Strasbourg and remained engrossed in magnetic research that had originated in Pierre Weiss's laboratory. Working alongside a team of researchers, many of whom had emigrated from occupied France, including Jacques Mehring, who, like Bertaut, hailed from the L.C.P., as well as Robert Forrer, Noël Felici, and Louis Weil, Bertaut's expertise in crystallography proved indispensable. Their collaborative efforts took place within Grenoble's Faculty of Science at the Fourier Institute, where Bertaut and Mehring fashioned a rudimentary X-ray device.

After the war, it was with the help of this team that Louis Néel founded the Laboratoire d'Electrostatique et de Physique du Métal (L.E.P.M.) in 1946, which was the first CNRS laboratory outside the Paris region. It included electrostatics under N. Felici, very low temperatures under L. Weil, magnetism under L. Néel and X-ray diffraction under E. F. Bertaut. Félix Bertaut, who had arrived in 1943 before the Liberation "without any qualifications", took over Erwin Lewy's qualifications in 1946 and obtained a research grant from the Centre National de la Recherche Scientifique (CNRS) under his wartime identity, "Félix Bertaut".

Félix Bertaut and crystallography (1946-2003)

In 1946, Félix Bertaut chose a new subject for his doctoral thesis: "X-ray studies of the dimensions of Bragg domains in polycrystalline powders. - Application to the study of the texture and structure of pyrophoric iron powders and their magnetic properties". In this thesis work, he first distinguished between the size of the grains themselves and their distribution. This knowledge of the grain size of iron powders was necessary for Louis Néel's magnetism studies, as Louis Weil had just succeeded in synthesising iron powders with small particles that are good materials for permanent magnets. Part of this thesis had an industrial outlet because these excellent iron-based magnets, produced by the local industry UGINE using waste from the buttons of the company ARaymond, were used in particular in bicycle dynamos.

Félix Bertaut submitted his thesis in 1949, with the great crystallographer André Guinier as examiner. At the time, this work was a highly original application of X-ray diffraction, and this type of X-ray diffraction studies of powder granulometry has since developed considerably, but the method established by Bertaut and at the same time by Warren and Averbach , known as the Bertaut-Warren-Averbach method, remains a classic and a cornerstone of this discipline.

Immediately after his thesis, Félix Bertaut developed the group at the L.E.P.M. that formed the basis of the X-ray department to carry out research in cristallography, a science that enables the atomic arrangements in solids to be determined using X-ray diffraction, with the aim of establishing the relationship between crystalline structure and magnetic properties. Next, Félix Bertaut and his group, along with Francis Forrat and Professor René Pauthenet, distinguished themselves with their work on garnet ferrites, from which the theory of antiferromagnetism and ferrimagnetism was built up. These garnets were the symbol of the joint work of L. Néel, F. Bertaut and R. Pauthenet: this is why E.F. Lewy-Bertaut had them engraved on his sword as an Academician. These ferrites are currently important materials for magnetic recording and microwave electronics (such as mobile phones).

E.F. Bertaut was involved in several other aspects of crystallography. He solved the structure of complex compounds such as the non-stoichiometric pyrrhotite, Fe_1-xS. He developed what is known as structure factor algebra. He made an enormous contribution to neutron crystallography. He extended the use of group theory in crystallography, particularly for magnetic structures. When the International Union of Crystallography (IUCr) decided to finalise the volume on the symmetry of space groups in the International Tables of Crystallography, he was a member of the ad hoc committee and contributed in particular to the definition of magnetic groups. He used the symmetry of crystals to propose all possible magnetic structures. This "Bertaut method" was very useful for complex structures, and even more so before the availability of computers. Of course, his students had to apply this method anyway. At the same time, he did not forget his training as a chemist and, in 'his' two laboratories, chemical syntheses of new materials continually fed into crystallographic studies, mainly for a better understanding of magnetism. One of his merits is that he was able to maintain close contact between theory and experimental applications.

In 1971, right after Louis Néel received the Nobel Prize for his groundbreaking investigations into antiferromagnetism, ferrimagnetism, and their practical applications, the L.E.P.M. laboratory underwent a transition, relocating adjacent to the newly established Centre d'Etude Nucléaire de Grenoble (C.E.N.G.), also founded by Néel. This shift unfolded within the premises of the former "Polygone" military complex, forming a consortium of C. N.R.S. research units. Guiding its trajectory from 1971 to 1982 was E.F. Bertaut, who initially assumed the role of Maître de Recherche and later ascended to the position of Directeur de Recherches at the CNRS. Even after entering a phase of "active retirement," Bertaut remained engaged in scholarly pursuits, serving as a referee for scientific journals specializing in crystallography and maintaining an active role as an Academician.

In 2007, in conjunction with the Centre de Recherche sur les Très Basses Températures (CRTBT), the Laboratoire de Magnétisme, and the Laboratoire d'Etudes des propriétés Electroniques (LEPES), this laboratory focused on crystallography became an important component of the Institut Néel at the C.N.R.S. - U.G.A.

Erwin Félix Bertaut and neutrons

In 1949, Félix Bertaut's research was turned upside down by a one-page publication in "Physical Review" by two Americans, Shull (later to win a Nobel Prize for this study) and Smart, which revealed the first magnetic structure obtained by neutron diffraction in manganese oxide MnO. The hypotheses formulated 15 years earlier by Louis Néel on antiferromagnetism were verified: magnetic orders could be observed in "neutron diffraction images". Louis Néel was enthusiastic and planned to build a neutron reactor in Grenoble. To this end, Félix Bertaut travelled to the United States in 1951, and then (after lengthy procedures due to McCarthyism) received a Fulbright grant in 1953 to continue his research in the United States for a year, where he joined Ray Pepinski's laboratory at State College in Pennsylvania. Pepinski gave him access to the Brookhaven atomic centre, where he visited the neutron diffraction facilities of Lester Corliss and Julius Hastings and learned about neutron techniques.

For some time, France and General De Gaulle had been in favour of setting up a nuclear research centre, and in 1955 Louis Néel, a reserve admiral who had the confidence of the French Army, provided decisive arguments (scientific themes and techniques) for the establishment of a Centre d'Etudes Nucléaires à Grenoble (C.E.N.G.) on the "Polygone" site. L. Néel bought the military land at the Polygone d'Artillerie for a symbolic 1 franc to create the Nuclear Research Centre, which he would direct. He asked E.F. Bertaut to set up a Neutron Diffraction Laboratory dedicated to crystallographic studies using neutron beams. E.F. Bertaut was in charge from 1958 to 1976, and from 1958 W. Koehler and L. Corliss joined him to introduce Grenoble researchers to neutron diffraction and design the first diffractometer. This and the next were installed at the Mélusine reactor (8 MW), followed by two others at the Siloe reactor (35 MW). This laboratory was the crucible for a generation of scientists familiar with neutrons, who would also work with the Centre de Saclay. It was also at this time that E.F. Bertaut, F. Forrat, P. Blum and R. Pauthenet made their mark with the discovery and study of garnet ferrites6-7, now essential materials for magnetic memories and high-frequency electronics. E.F. Bertaut and his laboratories gained international renown in crystallography, neutron diffraction and magnetism.

The international reputation of the Grenoble laboratories and E.F. Bertaut in crystallography, neutron diffraction and magnetism led to the first international conference on neutron scattering being held in Grenoble in 1963. It was during the banquet at this conference that the construction of a European high-flux neutron reactor was first suggested by Néel in a speech prepared by E.F. Bertaut.

Then, with the support of L. Néel, E.F. Bertaut promoted the project and convinced his German collaborators. He was certainly convincing - and it was the right idea at the right time, since the French and German peoples, under the leadership of De Gaulle and Adenauer, were at that time re-establishing friendly relations. So on 22 January 1963, the "Elysée Treaty" signed by Federal Chancellor Konrad Adenauer and the President of the French Republic, Charles de Gaulle, launched Franco-German cooperation. E. F. Bertaut was deeply pleased with this Franco-German collaboration and worked relentlessly to forge closer links with German crystallographers and chemists. He will be one of the ambassadors of the High Flux Reactor project, giving it scientific applications and a Franco-German support community. The success of neutron techniques enabled L. Néel and E. F. Bertaut to propose and obtain the construction of the Franco-German High Flux Reactor (ILL) in Grenoble in 1967.

This led to the creation of the high-flux neutron reactor. Grenoble was considered a major centre for magnetism under L. Néel and a capital of neutron diffraction under F. Bertaut, so the institute was built in Grenoble. Its name "Institut Laue-Langevin" (ILL) expresses the combination of crystallography and magnetism. Initially Franco-German, the ILL became European and was a key partner in the construction of the European Synchrotron Radiation Facility (ESRF) in Grenoble. This source of synchrotron radiation is used in a variety of fields including biology, medicine, chemistry, magnetism, high pressure, materials science via crystallography (and among its many applications) magnetic nanostructures, etc.

The ILL has now taken over from Grenoble's first reactors, and Bertaut's students (or his students' students) continue to develop this knowledge. The seeds sown by Néel, Bertaut and their colleagues have germinated and grown.

Research

E. F. Bertaut was an eclectic, highly cultured man who had learned Latin, Greek, French, English, law, music and then chemistry and crystallography and, as Professor André Guinier said, "Félix Bertaut is a mathematician who does crystallography". The author of several hundred publications, of which a hundred or so were by his sole name, often short notes in the Comptes Rendus de l'Académie des sciences or in Acta Crystallographica, and the head of two quite different laboratories, E.F. Bertaut was also an ardent apostle of the province and of diversity. He played a major role in turning a provincial town, Grenoble, into a European scientific centre.

Scientific distinctions and appointments

E.F. Bertaut's scientific reputation is international. He was a member of the IUCr executive committee between 1975 and 1981. He was co-founder of its "Neutron Diffraction" commission and co-founder and chairman of its "International Tables" and "Charge, Spin and Momentum Density" commissions. He was the IUCr representative on the Solid State Commission of the International Union of Pure and Applied Physics (IUPAP) between 1966 and 1972 and was secretary and then chairman of the Solid State Physics Section. He was editor or co-editor of numerous scientific journals. From 1958 to 1982, he was scientific advisor to various institutes: Commissariat à l'Energie Atomique (CEA), CNRS, ILL, and Max Planck Institut - Stuttgart). Knight of the Legion of Honour and Commander of the National Order of Merit, he has received several awards and has been appointed Professor honoris causa of various universities: Geneva, Frankfurt, Uppsala, Helsinki and Xanthi. He was elected a full member of the Académie des Sciences in 1979.

More information

Bibliography

• Erwin Félix Lewy-Bertaut (1913-2003), In memoriam published on the IUCr website.
• Erwin Félix Lewy-Bertaut, Notice nécrologique de l’Académie des Sciences, J. Villain (2004).
• Erwin Félix Lewy-Bertaut - Les Membres de l'Académie des sciences (academie-sciences.fr)
• La vie et l'oeuvre scientifique d’Erwin Félix Lewy-Bertaut, Séance publique Académie des Sciences du 8 novembre 2005, J-Cl. Pecker (2005)
• De Bergevin, F.; Hodeau, J. L.; Schweizer, J. (2004). "Erwin Félix Lewy-Bertaut (1913–2003)". Journal of Applied Crystallography. 37 (2): 349–350. doi:10.1107/S0021889804004376.
• Hahn, T. (2004). "Félix Bertaut, space groups and the International Tables for Crystallography". Journal of Applied Crystallography. 37 (2): 350–351. doi:10.1107/S0021889804004443.
• Férey, G.; Hodeau, J.-L. (2015). "The life and achievements of Erwin-Félix Lewy-Bertaut (1913–2003)". Physica Scripta. 90 (2): 028001. Bibcode:2015PhyS...90b8001F. doi:10.1088/0031-8949/90/2/028001. S2CID 119896912.
• Journée Scientifique « E.F. BERTAUT » May 2006, CNRS-Polygone, Grenoble.

References

1. Alfred Kastler, Nobel laureate for physics in 1994 “for the discovery and development of optical methods for studying hertzian resonances in atoms”.
2. Louis Néel, Nobel laureate for physics in 1970 “for fundamental work and discoveries concerning antiferromagnetism and ferrimagnetism which have led to important applications in solid state physics”.
3. * Néel, L. (1932). "Influence des fluctuations du champ moléculaire sur les propriétés magnétiques des corps" (PDF). Annales de Physique. 10 (18): 5–105. Bibcode:1932AnPh...10....5N. doi:10.1051/anphys/193210180005.
   • Néel, L. (1936). "Propriétés magnétiques de l'état métallique et énergie d'interaction entre atomes magnétiques" (PDF). Annales de Physique. 11 (5): 232–279. Bibcode:1936AnPh...11..232N. doi:10.1051/anphys/193611050232.
4. • Bertaut, F. (1949). "Signification de la dimension cristalline mesurée d'après la largeur de la raie Debye–Scherrer". Comptes rendus hebdomadaires des séances de l'Académie des sciences. 228: 187.
   • Bertaut, F. (1949). "Études aux rayons X de la répartition des dimensions des cristallites dans une poudre cristalline". Comptes rendus hebdomadaires des séances de l'Académie des sciences. 228: 492.
   • Bertaut, E. F. (1950). "Raies de Debye–Scherrer et repartition des dimensions des domaines de Bragg dans les poudres polycristallines". Acta Crystallographica. 3: 14–18. doi:10.1107/S0365110X50000045.
   • Bertaut, E. F. (1952). "Sur la correction de la transformée de Fourier d'une raie de Debye–Scherrer dans la mesure de dimensions cristallines". Acta Crystallographica. 5: 117–121. doi:10.1107/S0365110X5200023X.
5. • Warren, B. E.; Averbach, B. L. (1950). "The Effect of Cold-Work Distortion on X-Ray Patterns". Journal of Applied Physics. 21 (6): 595–599. Bibcode:1950JAP....21..595W. doi:10.1063/1.1699713.
   • Warren, B. E.; Averbach, B. L. (1952). "The Separation of Cold-Work Distortion and Particle Size Broadening in X-Ray Patterns". Journal of Applied Physics. 23 (4): 497. Bibcode:1952JAP....23Q.497W. doi:10.1063/1.1702234.
6. • Pauthenet, R.; Blum, P. (1954). "Étude thermomagnétique du ferrite de gadolinium". Comptes rendus hebdomadaires des séances de l'Académie des sciences. 239: 33.
   • Bertaut, F.; Forrat, F. (1956). "Structure des ferrites ferrimagnétiques des terres rares". Comptes rendus hebdomadaires des séances de l'Académie des sciences. 242: 382.
7. Bertaut, E. F. (1953). "Contribution à l'étude des structures lacunaires: La pyrrhotine". Acta Crystallographica. 6 (6): 557–561. doi:10.1107/S0365110X53001502.
8. • Bertaut, E. F. (1956). "Algèbre des facteurs de structure". Acta Crystallographica. 9 (9): 769–770. doi:10.1107/S0365110X56002096.
   • Bertaut, E. F.; Waser, J. (1957). "Structure factor algebra. II". Acta Crystallographica. 10 (9): 606–607. doi:10.1107/S0365110X57002169.
   • Bertaut, E. F. (1959). "IV. Algèbre des facteurs de structure". Acta Crystallographica. 12 (7): 541–549. doi:10.1107/S0365110X5900161X.
   • Bertaut, E. F. (1959). "V. Algèbre des facteurs de structure". Acta Crystallographica. 12 (8): 570–574. doi:10.1107/S0365110X59001682.
9. Bertaut, E. F. (1968). "Representation analysis of magnetic structures". Acta Crystallographica Section A. 24 (1): 217–231. Bibcode:1968AcCrA..24..217B. doi:10.1107/S0567739468000306.
10. Bertaut, E. F.; Wondratschek, H. (1971). "Ordering scheme for general positions in International Tables". Acta Crystallographica Section A. 27 (3): 298–300. Bibcode:1971AcCrA..27..298B. doi:10.1107/S056773947100069X.
11. Shull, C. G.; Smart, J. S. (1949). "Detection of Antiferromagnetism by Neutron Diffraction". Physical Review. 76 (8): 1256–1257. Bibcode:1949PhRv...76.1256S. doi:10.1103/PhysRev.76.1256.2.
12. B.N. Brockhouse & C.G. Shull, Nobel laureate for physics in 1994 "for pioneering contributions to the development of neutron scattering techniques for studies of condensed matter" to B.N. Brockhouse "for the development of neutron spectroscopy" and to C.G. Shull "for the development of the neutron diffraction"

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