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Why do we like magnetism?
It is fascinating (“on s’amuse”) We have witnessed two recent breakthroughs, which inspire our sponsors:
- 1. Lighter, stronger and more stable magnets
- 2. GMR hit the market at an unprecedented speed
Motivating ESM2009 Why do we like magnetism? Why do we need models? - - PowerPoint PPT Presentation
Motivating ESM2009 Why do we like magnetism? Why do we need models? - - PowerPoint PPT Presentation
Motivating ESM2009 Why do we like magnetism? Why do we need models? Peter de Chtel Institute of Nuclear Research Hungarian Academy of Sciences Debrecen, Hungary Why do we like magnetism? It is fascinating (on samuse) We have
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- 2. GMR hit the market at an unprecedented speed
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Nobel prize physics 2007 Giant magneto resistance
Albert Fert Peter Grünberg
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Why do we need models?
Why models, rather than the Real Thing? Microscopic level: relativistic and quantum- mechanical (Bohr - van Leeuwen theorem) Phenomenalogical level: nonlinear and irreversible (hysteresis)
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Magnetic field, Spin and orbital magnetic moments, Crystal electric field
John Michael Coey Today, Monday 01/09 14h
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Friday 04/09 14h
Mean field theory
Claudine Lacroix
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j i j i ij Heis
J H S S 2
.
j i z l z i ij Is j i y j y i x j x i ij XY
S S J H S S S S J H . 2 ); ( 2
The four bilinear model interactions
Heisenberg XY Ising
j i j i ij DM
H ) ( S S d
,
Dzyaloshinskii Moriya
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Thursday 03/09 11h
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Monte Carlo methods for magnetic systems Zoltán Néda
Sunday 06/09 15h
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Direct exchange
Parallel-spin electrons do not come too close to each other, that saves some Coulomb energy. Consequently, a given number of electrons claims a larger volume, if the spins are aligned.
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Superexchange
Delocalization is realized by hopping onto a neighbouring site, t is the hopping matrix element
,
d an
E E t E
2 d d an an an
E E t
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Wednesday 04/09 10h30 and 14h30
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Free electrons in a magnetic field
(external or molecular)
The Zeeman energy modifies the spectrum of available states, a rearrangement of occupancies occurs. In the new equilibrium state there is a net spin momentum and magnetisation.
S.V. Vonsovskii, Magnetism Vol.1 (1974)
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Magnetism of free electrons J.M.D. Coey Thursday 03/09 9h
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E.Yu. Tsymbal and D.G. Pettifor
- Phys. Rev. B 54 (1996) 15314
Density of states in cobalt and iron Co Fe
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Basics of electronic structure calculations for magnetic systems: Tight binding, LDA, DMFT Manual Richter Tuesday 01/09 16h and Thursday 04/09 11h
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Spin wave in an antiferromagnet in an external field H0
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Wulf Wulfhekel Monday 07/09 12h
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Magnetic anisotropy and how it can be controlled Dirk Sander
Thursday 03/09 12h
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Review of typical behaviours
- bserved in strongly correlated systems
Charles Simon Saturday 05/09 11h
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Spin fluctuation theory
for
itinerant magnetism
and introduction to
The physics of the Kondo effect
Mireille Lavagna Friday 04/09 16h and Saturday 05/09 9h
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Metal-insulator transition (Mott-Hubbard)
and
Magnetism and superconductivity
Jozef Spałek Saturday 05/09 14h30 and Sunday 06/09 9h
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Models in spin electronics
Bernard Diény Tuesday 08/09 14h and Thursday 10/09 10h30
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Magnetisation dynamics at different timescales: dissipation and thermal processes
Oksana Chubykalo-Fesenko Sunday 06/09 11h and Monday 07/09 11h
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Simple concepts of magnetisation reversal from materials to nanostructures
Olivier Fruchart Monday 07/09 9h, Tuesday 08/09 16h and Thursday 10/09 16h
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Preisach model of hysteresis in magnetic materials and FORC* based identification techniques
FORC: First-order Reversal Curves Alexandru Stancu Thursday 10/9 9h
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Transport in magnetic semiconductors
Tomasz Dietl Wednesday 09/09/09 14h
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Amusez-vous bien
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j i j i ij Heis
J H S S 2
j j ij i mf i B
J g S S B S 2
Molecular field in the Heisenberg model
) (
mf i i B mf
g H B B S
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