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Séance de cours

Anisotropie magnétique dans les matériaux cristallins

Dans cours

PHYS-407: Frontiers in nanosciences

The course covers relevant experimental and theoretical concepts in nanoscale science, from fundamental aspects like quantum tunneling and quantum size effects, to hot topics like quantum transport and nanoscale magnetism. ...

Description

Cette séance de cours explore le concept d'anisotropie magnétique dans les matériaux cristallins, en explorant comment l'orientation de l'aimantation est influencée par la structure cristalline. L'instructeur explique l'origine des moments magnétiques dans les atomes, les interactions entre les spins et les facteurs déterminant la direction préférée de l'aimantation dans les grains. La discussion couvre les effets de l'anisotropie de forme et de l'énergie d'anisotropie magnétique, cruciale pour comprendre la stabilité des systèmes magnétiques. La séance de cours aborde également le tunnelage quantique de l'aimantation et les techniques expérimentales utilisées pour mesurer le spin et les moments orbitaux séparément.

Enseignant·e·s (4)

Marina Pivetta

Klaus Kern

Klaus Kern is Professor of Physics at EPFL and Director and Scientific Member at the Max-Planck-Institute for Solid State Research in Stuttgart, Germany. He also is Honorary Professor at the University of Konstanz, Germany. His present research interests are in nanoscale science, quantum technology and in microscopy at the atomic limits of space and time. He holds a chemistry degree and PhD from the University of Bonn and a honorary doctors degree from the University of Aalborg. After his doctoral studies he was staff scientist at the Research Center Jülich and visiting scientist at Bell Laboratories, Murray Hill before joining the Faculty of EPFL in 1991 and the Max-Planck-Society in 1998. Professor Kern has authored and coauthored close to 700 scientific publications, which have received nearly 60‘000 citations. He has served frequently on advisory committees to universities, professional societies and institutions and has received numerous scientific awards and honors, including the 2008 Gottfried-Wilhelm-Leibniz Prize and the 2016 Van‘t Hoff Prize. Prof. Kern has also educated a large number of leading scientists in nanoscale physics and chemistry. During the past twenty-five years he has supervised one hundred PhD students and sixty postdoctoral fellows. Today, more than fifty of his former students and postdocs hold prominent faculty positions at Universities around the world.

Magalí Alejandra Lingenfelder

Magalí Lingenfelder is currently leading the Max Planck-EPFL Laboratory for Molecular Nanoscience. Her vision is to create atomically tailored interfaces for applications in two distinct areas of urgent technological and societal relevance: energy conversion and smart antimicrobial interfaces. To access the nanoscale, her group uses a combination of state-of-the-art scanning probe microscopy and solid state spectroscopy, allowing the study of kinetic processes in-situ under liquid flow and potential control conditions (operando electrocatalysis). She made seminal contributions to the field of metal-organic coordination networks on solid surfaces, and received the Otto Hahn medal in 2008 for the microscopic understanding of the chiral recognition process with submolecular resolution. She is a committed mentor, and since her relocation from the Lawrence Berkeley National Laboratory, USA to EPFL in 2013, she directed 3 MSc. theses, 4 PhD theses and 4 postdocs. She advocates for problem-oriented interdisciplinary research: she led 5 international research consortiums, delivered over 40 invited presentations and organized 9 conferences and 4 doctoral schools. In 2018, the Royal Society of Chemistry included her work in the first collection “Celebrating Excellence in Research: 100 Women of Chemistry”.

Source officielle

Proximité ontologique

Physique

Physique de la matière condensée: Transition de phase

Concepts associés (17)

Anisotropie magnétique

Une anisotropie magnétique est présente lorsque les propriétés magnétiques d'un système sont orientées selon des axes privilégiés. C'est le cas dans les matériaux ferromagnétiques, où l’aimantation suit des directions privilégiées appelées axes de facile aimantation. Dans les matériaux cristallins, il existe des directions selon lesquelles il est facile d'aimanter le cristal (axes faciles), et des directions de difficile aimantation, on parle d'anisotropie magnéto-cristalline.

Susceptibilité magnétique

La susceptibilité magnétique désigne une propriété d'un matériau qui caractérise la faculté de celui-ci à s'aimanter sous l'effet d'une excitation magnétique émise par un champ. C'est une grandeur sans dimension qu'on note en général par le symbole , ou simplement s'il n'y a pas d'ambiguïté avec la susceptibilité électrique dans le texte. Tout matériau est composé au niveau microscopique d'atomes liés ensemble, chacun de ces atomes pouvant être vu comme un aimant élémentaire si l'on ne s'intéresse qu'aux propriétés magnétiques.

Magnetocrystalline anisotropy

In physics, a ferromagnetic material is said to have magnetocrystalline anisotropy if it takes more energy to magnetize it in certain directions than in others. These directions are usually related to the principal axes of its crystal lattice. It is a special case of magnetic anisotropy. In other words, the excess energy required to magnetize a specimen in a particular direction over that required to magnetize it along the easy direction is called crystalline anisotropy energy.

Magnetic domain

A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moments of the atoms are aligned with one another and they point in the same direction. When cooled below a temperature called the Curie temperature, the magnetization of a piece of ferromagnetic material spontaneously divides into many small regions called magnetic domains. The magnetization within each domain points in a uniform direction, but the magnetization of different domains may point in different directions.

Aimantation

Dans la langue courante, l'aimantation d'un objet est le fait qu'il soit aimanté ou bien le processus par lequel il le devient. En physique, l'aimantation est de plus, et surtout, une grandeur vectorielle qui caractérise à l'échelle macroscopique l'orientation et l'intensité de son aimantation au premier des deux sens précédents. Elle a comme origine les courants microscopiques résultant du mouvement des électrons dans l'atome (moment magnétique orbital des électrons), ainsi que le moment magnétique de spin des électrons ou des noyaux atomiques.

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Séances de cours associées (39)

Anisotropie magnétique: principes fondamentaux et applications

Explore l'énergie d'anisotropie magnétique, les moments orbitaux, l'aimantation des bits, le superparamagnétisme et l'ingénierie à l'échelle atomique dans les nanostructures.

Interactions magnétiques : ferromagnétisme et échange

Couvre le ferromagnétisme, l'antiferromagnétisme et le paramagnétisme, expliquant les interactions d'échange et les domaines magnétiques.

Résonance antiferromagnétique

Explore la transition spin-flop, la susceptibilité et la résonance magnétique chez les antiferromagnétiques.

Magnétisme: Matériaux et domaines

Explore l'induction, les équations de Maxwell, les matériaux magnétiques, l'électromagnétisme et les cycles d'hystérésis chez les ferromagnétiques.

Science des matériaux des matériaux magnétiques

Couvre la science des matériaux des matériaux magnétiques, en mettant l'accent sur les propriétés, les concepts et l'optimisation pour les applications fonctionnelles.

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Stefano Rusponi

Education: • 1999 Doctoral degree in Physics obtained at the Physics Department, University of Genova PhD thesis title: “STM study of nanostructures induced by ion sputtering on noble metals”. • 1994 University degree in Physics achieved at the Physics Department, University of Genova. Final mark: 110/110 cum laude Diploma thesis title: “A project for a new method of EELS spectroscopy”. • 1988 High school at the Liceo Scientifico G. P. Vieusseux in Imperia. Final mark: 60/60. Research career plan: • 2016 – present MER: Ecole Polytechnique Fédérale de Lausanne (EPFL) in the group of Prof. Harald Brune • 2003 – 2016: 1er. Assistant: Ecole Polytechnique Fédérale de Lausanne (EPFL) in the group of Prof. Harald Brune • 2000-2003: Assistant: Ecole Polytechnique Fédérale de Lausanne (EPFL) under the direction of Prof. Harald Brune • 1999-2000: Research associate: Max-Planck-Institut of Stuttgart under the direction of Prof. Klaus Kern Miscellaneous of professional activities: a) Review panel • Member of the Elettra proposal review panel • Member of the committee of the EDPY doctoral school in Physics at the EPFL b) Co-worker in the building of the X-Treme beamline: c) Referee for scientific journals: • Nat. Commun., Phys. Rev. Lett., Phys. Rev. B, J. Appl. Phys., Surf. Sci., J. Magn. Magn. Mater. Funding record a) Funding awarded • Quantum Properties of Nanostructures at Surfaces, FNS 200020-157081/1; (01/10/2014 – 31/09/2017); total amount attributed: 832'558 CHF; co-applicant • Controlling magnetic anisotropy by interfacial coupling, FNS 200021_146715/1; (01/01/2014 – 31/12/2016); total amount attributed: 367'800 CHF; co-applicant • Self-assembled bi-metallic magnetic pillar superlattices with enhanced blocking temperature, SER C10.0135; (01/08/2011 – 01/08/2013); total amount attributed: 170'000 CHF; co-applicant • Magnetic and Catalytic Properties of Surface Supported Metallic Nanostructures, FNS 200020-120493/1; (01/04/2008 – 31/03/2010); total amount attributed: 402'669 CHF; co-applicant • Magnetic and Catalytic Properties of Surface Supported Metallic Nanostructures, FNS 200020-112322/1; (01/04/2006 – 31/03/2008); total amount attributed: 347'633 CHF; co-applicant b) Approved proposals for the allocation of beamtime Swiss Light Source (SLS): main proposer: 9 co-proposer: 4 Elettra: main proposer: 5 co-proposer: 1 European Synchrotron Radiation Facility (ESRF): main proposer: 2 co-proposer: 11 Student supervisor • Co-director of PhD thesis: 4 PhD students

Dimitris Mousadakos: Seeking the smallest room temperature magnets; (in progress)
Romana Baltic: Controlling single atom magnetic anisotropy by interfacial coupling; (in progress)
Alberto Cavallin: Growth and magnetism of nanostructures investigated by STM, MOKE, and XMCD; (Oct. 2013), Thèse N°5941
Sergio Vlaic: Magnetism and atomic scale structure of bimetallic nanostructures at surfaces; (Dec. 2012), Thèse N° 5625

• Supervisor of PhD thesis (without co-direction): 4 PhD students

Anne Lehnert: Magnetism of individual adatoms and of epitaxial monolayers; (Jun. 2009), Thèse N° 4411
Geraud Moulas: Growth and magnetism of 2D bimetallic nanostructures; (Dec. 2008), Thèse N° 4231
Philipp Buluschek: Submonolayer growth of cobalt on metallic and insulating surfaces studied by scanning tunneling microscopy and kinetic Monte-Carlo simulations; (Nov. 2007), Thèse N° 3944
Nicolas Weiss: Propriétés magnétiques de nanostructures de Co adsorbées; (Apr. 2004), Thèse N° 2980

• Supervisor of Master thesis: 6 students • Supervisor of semester projects: 9 students • PhD thesis referee: 2 students

Concepts associés (17)

Anisotropie magnétique

Susceptibilité magnétique

Magnetocrystalline anisotropy

Magnetic domain

Aimantation

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