Magnetism in Condensed Matter

I Introduction

• Basic definitions
• Bohr-van Leeuwen Theorem
• Demagnetizing field
• 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
• Tutorial 1

II Magnetism of free atoms/ions

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

III Atoms in crystalline environment

• 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
• Electron Spin Resonance: Extra Slide
• Jahn-Teller effect
• Link: H. A. Jahn, E. Teller, Original Work: p. 220 of the Proceedings of the Royal Soc. 161
• Orbital order

IV Magnetic exchange interactions

Extra slides: Photoemission Spectroscopy

• Kinetic exchange
• Electron-electron correlations, t, U
• 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
• Dzyaloshinskii-Moriya exchange
• X-ray absorption spectroscopy
• Resonant X-ray scattering
• Link: Resonant scattering beamline at HASYLAB@DESY
• Link: Orbital order in La7/8Sr1/8MnO3

V Magnetism in metals

• Corrected script page: XMCD
• Reminder: The free electron gas
• Pauli susceptibility and T-corrections
• Band magnetism, Stoner model
• Stoner enhancement of the susceptibility
• Link: Biography E.C. Stoner/U Leeds
• Circular magnetic x-ray dichroism XMCD
• XMCD tutorial from Berkeley ESG group at ALS
• RKKY interaction
• Friedel oscillations
• Landau levels
• Link: Calculate Landau levels (java applet G. Graf)
• Landau diamagnetism
• Link: Tutorial Manuscript by S. Teitel on the theory of T=0 Landau diamagnetism
• De Haas-van Alphen effect

VI Collective Phenomena, Micro- and Nanomagnetism

• Phase transitions
• Landau theory
• Ferromagnetic order
• FM Spin waves, Bloch's T3/2-law
• Antiferromagnetic order
• Spin-Flop, Spin-Flip
• AFM spin waves
• Magnetic frustration
• Link: R. Moessner: Tutorial on frustrated magnetism
• Spin glasses
• Single domain magnets
• Superparamagnetism
• Magnetic hyperthermia
• Link: Nanomagnet-based anti-cancer therapy: MAGFORCE company
• Link: Magnetic hyperthermia @ KIP

VII Magnetoresistive effects

• 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.
• Tunneling MR (TMR)
• (Colossal Magnetoresistance CMR) cf. chapter V
• Magnetic data storage, read/write heads

VIII A slide show for the final: Molecular magnetism