Lecture content & slides & additional information

I. Introduction (slides)

• Link: More is different: P.W. Anderson, Science 1972
• General motivation and introduction
• Basic definitions
• Generation of magnetic fields
• Link: High magnetic fields labs: (1) Tallahassee/Los Alamos (US), (2) LNCMI Toulouse/Grenoble, (3) FZ Dresden-Rossendorf)
• Link: Video from LNCMI describing pulsed field magnets
• Methods for measuring magnetic properties
• Bohr-van Leeuwen Theorem
• Demagnetizing field

II. Magnetism of free atoms/ions (slides)

• Hamiltonian of atoms in an external magnetic field
• Perturbation theory for treating effects of B-field
• Larmor diamagnetism
• Paramagnetism of free atoms, Curie law
• Van Vleck paramagnetism
• Spin-orbit coupling
• Hund's rules
• Hyperfine interaction

III. Cooperative phenomena (slides)

• Phase transitions
• Landau theory
• Ferromagnetic order
• FM Spin waves, Bloch's T^3/2-law
• Animation (ext. link): FM spin wave
• Antiferromagnetic order
• Spin-Flop, Spin-Flip
• Skript: Spin Flop
• AFM spin waves
• Animation SLAC (ext. link): AFM spin waves
• Magnetic frustration
• Link: R. Moessner: Tutorial on frustrated magnetism
• Spin glasses

IV. Magnetism in metals (slides)

• Reminder: The free electron gas
• Pauli susceptibility and T-corrections
• Script: Pauli susceptibility T-corrections
• Band magnetism, Stoner model
• Stoner enhancement of the susceptibility
• Link: Biography E.C. Stoner/U Leeds
• Circular magnetic x-ray dichroism XMCD
• lecture notes: XMCD
• XMCD tutorial from Berkeley ESG group at ALS
• Localized magnetic moments in metals
• Kondo effect
• Link: About Jun Kondo and his discovery
• RKKY interaction
• Friedel oscillations
• Landau levels
• Self studies: Landau diamagnetism
• Link: Nobel prize 1962 - Lev Landau
• De Haas-van Alphen effect

V. Micro- and Nanomagnetism (slides)

• Single domain magnets
• Superparamagnetism
• Magnetic hyperthermia
• Link: Commercial nanomagnet-based anti-cancer therapy
• Link: Magnetic hyperthermia @ KIP
• Exchange bias

VI. Magnetoresistive Effects and Spinelectronic Devices (slides)

• Positive Magnetoresistance
• Negative Magnetoresistance due to spin order
• Anisotropic MR (AMR)
• Giant Magnetoresistance (GMR)
• Link Animation GMR (FZ Jülich)
• Link Nobel Prize Fert, Grünberg, Royal Swedish Acad. Sc.
• Link: Explanation of GMR@Nobelprize.org
• Tunneling MR (TMR)
• Colossal Magnetoresistance CMR) cf. chapter IX
• Magnetic data storage, read/write heads

VII. Atoms in crystalline environment (slides)

• Crystal fields
• Symmetry, group theory and the Hamiltonian
• Link: Images representing atomic orbitals
• Link: Character tables and symmetry reduction tool
• Link: R.C. Powell: Symmetry, Group Theory, and the Physical Properties of Crystals: via HEIDI)
• Splitting of 3d-levels in the CF
• High-spin/low-spin states
• Quenching of the orbital momentum
• Effect of spin-orbit coupling
• Spin Hamiltonian, g-factor
• Jahn-Teller effect
• Link: H. A. Jahn, E. Teller, Original Work: p. 220 of the Proceedings of the Royal Soc. 161
• Orbital order

VIII Electronic correlation, Hubbard model, Mott insulators (slides)

Advanced further reading: M. Imada, A. Fujimori, Y. Tokura: Metal-Insulator transitions, Rev. Mod. Phys. 70, 1039–1263 (1998)

• General idea of the Mott transition
• Bandwidth controlled Mott transition
• The example of NiO
• Hubbard model
• One-band Hubbard model
• Which electrons are we talking about?
• Hubbard subbands
• The example of RNiO3
• Mott-Hubbard vs. charge transfer insulators
• Bandwidth-controlled metal-insulator transition
• Zaanen-Sawatzki-Allen Schema
• Link: Zaanen-Sawatzki-Allen, PRL 1985
• Link: Experimental Zaanen-Sawatki-Allen schema: Boquet1996

IX Exchange Interactions (slides)

• Kinetic exchange
• Goodenough-Kanamori-Anderson rules
• Inelastic neutron scattering
• Link: Thermal 3-axis spectrameters @ ILL Grenoble
• Kugel-Khomskii exchange, orbital order
• Double exchange
• Link: C. Zener's initial paper
• Resonant X-ray scattering
• Link: Resonant Inelastic X-Ray Scattering  at ESRF Grenable
• Link: Orbital order in La7/8Sr1/8MnO3

X One-dimensional quantum magnets (slides)

• Educational review on spin liquids (in German): Das Wechselspiel magnetischer Anregungen in Spinflüssigkeiten (Uhrig, Grüninger)
• Non-interacting dimers
• RVB state
• Mermin-Wagner theorem
• For experts: Theory tutorial by H. Wagner, U. Schollwoeck on the MW theorem
• Uniform AFM 1D Heisenberg chain
• Inelastic Neutron Scattering
• S=1 Haldane chain
• Link: Haldane, PRL 1983
• 1D heat transport
• Anisotropic Heisenberg chain
• Alternating Heisenberg chain
• Spin-Peierls transition