or not ? This is NOT the question Everything is magnetic How ?

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Text of or not ? This is NOT the question Everything is magnetic How ?

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Slide 2 or not ? This is NOT the question Slide 3 Everything is magnetic How ? Slide 4 macroscopic world atomic or molecular world wonder world meter nano meter mole molecule 1 / 1 000 000 000 = 10 -9 10 -9 110 +23 Slide 5 macroscopic world atomic or molecular world wonder world Lewis Carroll, Through the looking-glass, Penguin Books, London, 1998 Illustrations by John Tenniel Slide 6 macroscopic world atomic or molecular world wonder world quantum macro Slide 7 N S macroscopic world traditional, classical magnets macro Slide 8 A pioneering experiment by M. Faraday Farady lines of forces about magnetic flux N S macroscopic world macro Courtesy Prof. Peter Day, the RI ; See also : The Philosopher s Tree,The Institute of Physics Publishing, Bristol, 1999) Slide 9 Courtesy Prof. Frank James, the RI Slide 10 M. Faradays magnetic laboratory Courtesy Prof. Frank James, the RI Slide 11 M. Faraday in his laboratory Courtesy Prof. Frank James, the RI Slide 12 macroscopic world traditional magnets N S N S attraction N S N S macro Slide 13 macroscopic world traditional magnets N S repulsion N S N S N S macro Slide 14 macroscopic world looking closer to the magnetic domains S N many sets of domains many sets of atomic magnetic moments macro quantum Slide 15 permanent magnets micron particles nanoparticlesclusters molecular clusters individual spins Physics : Macroscopic Mesoscopic Nanoscopic multi - domain nucleation, propagation and annihilation of domain walls single - domain uniform rotation curling magnetic moment quantum tunneling, quantization quantum interference Wolfgang Wernsdorfer, Grenoble macro quantum Slide 16 Lewis Carroll, Alices Adventures in Wonderland, Penguin Books, London, 1998 Illustrations by John Tenniel No ! no ! The adventures first said the Gryphon in an impatient tone : explanations take such a dreadful time. Slide 17 Everyday life is full of useful magnets which traditionally take the form of three-dimensional solids, oxides, metals and alloys macro Magnets Domains Curie Temperature Slide 18 The magnetic moments order at Curie temperature Paramagnetic solid : thermal agitation (kT) larger than the interaction (J) between molecules Solid, Magnetically Ordered thermal agitation (kT) weaker than the interaction (J) between molecules A set of molecules / atoms : kT > J T C kT J Magnetic Order Temperature or Curie Temperature Slide 19 Magnetic Order : ferro-, antiferro- and ferri-magnetism + = Ferromagnetism : Magnetic moments are identical and parallel + = 0 Antiferromagnetism : Magnetic moments are identical and anti parallel + = Ferrimagnetism (Nel) : Magnetic moments are different and anti parallel Slide 20 Magnetization of nanoparticles of Prussian Blue analogues, (A. Bleuzen, W. Werndorfer) MicroSQUID, 4 K Slide 21 Magnetization of nanoparticles of Prussian Blue analogues, (A. Bleuzen, W. Werndorfer) MicroSQUID, 4 K Remnant magnetization Coercive Field Slide 22 Fernande Olivier, Loving Picasso, H.N. Abrams Publishers, New York, 2001, p.139 He seemed to give off a radiance, an inner fire, and I coulnt resist this magnetism Slide 23 How magnetism comes to molecules ? the different faces of the electron Slide 24 Origin of Magnetism the electron * I am an electron rest mass m e, charge e -, magnetic moment B everything, tiny, elementary quantum * but do not forget nuclear magnetism ! Slide 25 Origin of Magnetism e-e- Orbital magnetic moment Intrinsic magnetic moment due to the spin quantum spin = g s x B x s B s = 1/2 orbital = g l x B x total = orbital + spin orbital spin Slide 26 Origin of Magnetism in molecules quantum electrons * in atoms in molecules * forgetting the nuclear magnetism Slide 27 Dirac Equation http://www-history.mcs.st-and.ac.uk/history/PictDisplay/Dirac.html 19281905 Nobel Prize 1933 The Principles of Quantum Mechanics, 1930 Slide 28 Lewis Carroll, Through the Looking-Glass, Penguin Books, London, 1998 Illustrations by John Tenniel When I use a word, Humpty Dumpty said, it just means what I choose it to mean neither more nor less The question is, said Alice, whether you can make words mean so different things The question is, said Humpty Dumpty, which is to be master that's all. Representations, Models, Analogies Slide 29 l = 0123 s p d angular representation Electron : corpuscle and wave Wave function or orbital n, l, m l Slide 30 Vacant Doubly occupied Orbitals Energy Diagramme Singly occupied Electron : also an energy level Slide 31 Singly occupied Nitrogen Monoxyde NO Nitronylnitroxyde Electron : also a spin ! Up Down Doubly occupied Paramagnetic S = 1/2 Diamagnetic S = 0 Slide 32 Paul Klee, Th orie de l art, Deno l, Paris An Isolated Spin Analogy : Analogy : Spin and Arrow Slide 33 Spin in Maya World ? Uxmal, Palacio del Gobernador, Mayab, Yucatan, July 2004 Slide 34 Molecules are most often regarded as isolated, non magnetic, creatures Dihydrogen diamagnetic Spin S = 0 Slide 35 the dioxygen that we continuously breathe is a magnetic molecule paramagnetic, spin S =1 Two of its electrons have parallel magnetic moments that shapes aerobic life and allows our existence as human beings orthogonal molecular orbitals Slide 36 macro when dioxygen is in an excited state it can becomes a singlet (spin S=0) and strange reactivity appears sometines useful (glow-worm ) Paramagnetic O 2 Luminol Light Slide 37 More complex molecular frameworks called metal complexes built from transition metal and molecules are able to bear up to five or seven electrons with aligned magnetic moments (spins) Slide 38 Slide 39 Transition Elements quantum Slide 40 Mononuclear complex ML 6 E Splitting of the energy levels Slide 41 How large is the splitting ? High spin L = H 2 O [C 2 O 4 ] 2- Low spin L = CN- Weak FieldStrong FieldIntermediate Field Temperature Dependent Spin Cross-Over Slide 42 macro The complexes of transition metal present often delicate and beautiful colours depending mostly on the splitting of the d orbitals Colours in water Geometry changes Spin changes h Slide 43 story of jumping electrons and moving spins Slide 44 two blue solutions Slide 45 [Co II (H 2 O) 6 ] 2+ + Methylene Blue KCN + Methylene Blue Slide 46 Slide 47 one yellow solution Slide 48 blue + blue = yellow ! [Co III (CN) 6 ] 3- + Methylene Reduced Colorless Slide 49 [Fe II (H 2 O) 6 ] 2+ pale green Fe II (o-Phen) 3 ] 2+ bright red S=0 S=2 Slide 50 Low spin, chiral, Fe II (bipyridine) 3 ] 2+ Slide 51 Playing with ligands, the chemist is able to control the spin state Slide 52 Review by Philipp Gtlich et al. Mainz University Angewandte Chemie 1994 Slide 53 Spin Cross-Over A Fe(II) Chain with spin cross-over Triazole substituted Ligand (R) ; insulated by counter-anions Many groups : Leiden, Mainz, Kojima, O. Kahn, C. Jay, Y. Garcia, ICMC Bordeaux 4+ Slide 54 Curie Law M T = Constant M T n (n+2) /8 if n = 4, M T 3 ! Slide 55 Spin Cross-Over Bistability Domain The system remembers its thermal past ! Room Temperature O. Kahn, C. Jay and ICMC Bordeaux Red 3 0 Slide 56 macro Hysteresis allows bistability of the system and use in display, memories Spin and colour changes Slide 57 Spin Cross-over Display Device (1)(2) (3) Display Connections O. Kahn, J. Krber, C. Jay Adv. Mater. 1992, 718 Kahn O., La Recherche, 1994, 163 Joule and Peltier Elements Compound in Low spin state (Thin Layer) Slide 58 O. Kahn, C. Jay and ICMC Bordeaux From the molecule to the material and to the device Slide 59 From J.F. Letard, ICMC Bordeaux Red White Slide 60 O. Kahn, Y. Garcia, Patent Slide 61 May we go further and dream of molecular magnets i.e. low density, biocompatible transparent or colourful magnets ?