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Erwin-Félix Lewy-Bertaut (9 February 1913 – 6 November 2003), also known separately as Erwin Lewy and Félix Bertaut, or E. F. Bertaut, was a French scientist renowned internationally for his work in the fields of neutron scattering and crystallography.

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 held positions of responsibility in the main international crystallography and physics organisations. He was a member of the French Academy of Sciences.

Biography

Lewy-Bertaut was born with the name Erwin Lewy to Jewish parents in Leobschütz of Silesia (then in Germany). 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 at the University of Freiburg and subsequently in University of 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-Bertaut left for Bordeaux, France. 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.

Lewy-Bertaut acquired French citizenship in 1936. In February 1939, fully aware of the peril of Nazism, he relocated his family to Talence, near Bordeaux and 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, and he adopted this name permanently. Lewy-Bertaut was later employed as a chemical engineer in the unoccupied region in Barbaste, where he focused on enhancing the durability of bicycle brakes crafted from agglomerated cork. To elude police inspections and evade mandatory labor service, he went to Paris, where he collaborated with Marcel Mathieu at the Central Laboratory for Powders (L.C.P.). Subsequently, he partnered with Emmanuel Grison, who tutored him in the utilization of the International Tables for 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, who was temporarily withdrawn from the University of Strasbourg and remained engrossed in magnetic research that had originated in Pierre Weiss's laboratory. After the war, Louis Néel founded the Laboratoire d'Electrostatique et de Physique du Métal (now Institut Néel) in 1946, which was the first CNRS laboratory outside the Paris region. It included electrostatics under Noël Felici, very low temperatures under Louis Weil, magnetism under Louis Néel, and X-ray diffraction under Lewy-Bertaut. Lewy-Bertaut also 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".

In 1946, Lewy-Bertaut conducted his thesis work under the supervision of Louis Néel. 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. Lewy-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, Lewy-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).

Lewy-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. 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. 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.

In 1949, Félix Bertaut's research encountered a transformative moment, triggered by a one-page publication in "Physical Review" authored by two Americans: Shull (later a Nobel Prize laureate for this work) and Smart. Their work unveiled the inaugural magnetic structure derived from neutron diffraction, specifically in manganese oxide MnO. The notions proposed 15 years earlier by Louis Néel concerning antiferromagnetism underwent validation, as magnetic order could be observed on neutron diffraction images. Néel's fervor was palpable, fueling his aspiration to construct a neutron reactor in Grenoble. Félix Bertaut embarked on a 1951 journey to the United States to realize these ideas. After navigating prolonged procedures necessitated by McCarthyism, he secured a Fulbright grant in 1953, allowing him to conduct research for a year in the U.S. Joining Ray Pepinski's laboratory at State College, Pennsylvania, Bertaut accessed the neutron diffraction facilities at the Brookhaven atomic center. Here, he acquainted himself with neutron methodologies under the guidance of Lester Corliss and Julius Hastings.

For a considerable duration, France, led by General De Gaulle, advocated for the establishment of a nuclear research center. In 1955, Louis Néel, a reserved admiral endowed with the confidence of the French Army, presented compelling rationale (both in terms of scientific themes and techniques) that substantiated the foundation of the Centre d'Etudes Nucléaires à Grenoble (C.E.N.G.) at the "Polygone" site. Néel procured the military land within the Polygone d'Artillerie for the nominal sum of 1 franc, a gesture that facilitated the inception of the Nuclear Research Centre, which he was entrusted to lead. He entrusted E.F. Bertaut with the task of establishing a Neutron Diffraction Laboratory dedicated to crystallographic inquiries through neutron beams. Bertaut helmed this initiative from 1958 to 1976, enlisting the expertise of W. Koehler and L. Corliss in 1958 to familiarize Grenoble researchers with neutron diffraction techniques and to design the inaugural diffractometer. These instruments found homes at the Mélusine reactor (8 MW), later joined by two more at the Siloe reactor (35 MW). This laboratory functioned as a crucible, shaping a generation of scientists adept in neutron manipulation, many of whom collaborated with the Centre de Saclay. Concurrently, E.F. Bertaut, F. Forrat, P. Blum, and R. Pauthenet achieved prominence through their exploration and examination of garnet ferrites — a class of materials pivotal in magnetic memory and high-frequency electronics. In the realm of crystallography, neutron diffraction, and magnetism, E.F. Bertaut and his laboratories garnered international acclaim.

The international reputation of Grenoble's laboratories and that of E.F. Bertaut in the domains of crystallography, neutron diffraction, and magnetism culminated in the inauguration of the inaugural international conference on neutron scattering in 1963. Within the convivial atmosphere of the conference banquet, a monumental proposal was unveiled: Louis Néel, through a speech meticulously crafted by E.F. Bertaut, introduced the idea of constructing a high-flux neutron reactor on a European scale.

Harnessing the backing of Néel and driven by his persuasive prowess, E.F. Bertaut championed the initiative and garnered the support of his German counterparts. His persuasion bore fruit, timely aligning with the rapprochement between the French and German populations under the leadership of De Gaulle and Adenauer. In the backdrop of this diplomatic atmosphere, the "Elysée Treaty," signed on 22 January 1963 by Federal Chancellor Konrad Adenauer and French President Charles de Gaulle, launched a new era of Franco-German cooperation. E.F. Bertaut's gratification was profound, and he tirelessly toiled to weave stronger bonds with German crystallographers and chemists. He emerged as a fervent advocate for the High Flux Reactor project, not only endowing it with scientific purpose but also fostering a Franco-German community of support. This concerted endeavor culminated in the realization of the Franco-German High Flux Reactor (ILL) in Grenoble, a monumental achievement facilitated by the triumph of neutron techniques pioneered by Louis Néel and E.F. Bertaut.

This milestone marked the inception of the high-flux neutron reactor. With Grenoble already established as a prominent hub for magnetism under Néel's guidance and a focal point for neutron diffraction under Bertaut's influence, the logical site for the institute's establishment was Grenoble itself. This entity was christened the "Institut Laue-Langevin" (ILL), symbolizing the confluence of crystallography and magnetism. What began as a Franco-German initiative later evolved into a pan-European endeavor, with ILL playing a pivotal role in the establishment of the European Synchrotron Radiation Facility (ESRF) in Grenoble. The ESRF, a source of synchrotron radiation, finds application across an array of disciplines including biology, medicine, chemistry, magnetism, high pressure studies, and materials science encompassing crystallography, and notably, magnetic nanostructures.

As the ILL succeeded Grenoble's earlier reactors, Bertaut's intellectual legacy has been perpetuated through successive generations of his students and their disciples who continue to advance this invaluable knowledge.

Honors and distinctions

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.

Further reading

• 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)
• Journée Scientifique « E.F. BERTAUT » May 2006, CNRS-Polygone, Grenoble.

References

1. ^ De Bergevin, F.; Hodeau, J. L.; Schweizer, J. (2004-04-01). "Erwin Félix Lewy-Bertaut (1913–2003)". Journal of Applied Crystallography. 37 (2): 349–350. doi:10.1107/S0021889804004376. ISSN 0021-8898.
2. Férey, Gérard; Hodeau, Jean-Louis (2015-02-01). "The life and achievements of Erwin-Félix Lewy-Bertaut (1913–2003)". Physica Scripta. 90 (2): 028001. doi:10.1088/0031-8949/90/2/028001. ISSN 0031-8949.
3. "CTHS - LEWY Erwin dit Félix BERTAUT". cths.fr.
4. Hahn, Theo (2004-04-01). "Félix Bertaut, space groups and the International Tables for Crystallography". Journal of Applied Crystallography. 37 (2): 350–351. doi:10.1107/S0021889804004443. ISSN 0021-8898.
5. Leoni, M. (2019). "The Warren–Averbach method and its variations". urn:isbn:978-1-118-41628-0. H: 288–303. doi:10.1107/97809553602060000951.
6. Bertaut, E. F. (1953). "Contribution à l'étude des structures lacunaires: La pyrrhotine". Acta Crystallographica. 6 (6): 557–561. Bibcode:1953AcCry...6..557B. doi:10.1107/S0365110X53001502.
7. 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.
8. 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.
9. 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.
10. 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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