84539 - MAGNETISM AND SUPERCONDUCTIVITY

Scheda insegnamento

  • Docente Samuele Sanna

  • Crediti formativi 6

  • SSD FIS/03

  • Modalità di erogazione In presenza (Convenzionale)

  • Lingua di insegnamento Inglese

  • Orario delle lezioni dal 05/10/2017 al 21/12/2017

Anno Accademico 2017/2018

Conoscenze e abilità da conseguire

At the end of the course the students learn the basic quantum phenomena occurring in magnetic and superconducting materials and several experimental techniques employed to study these properties, both on macroscopic (e.g. magnetometry) and microscopic scale (e.g. nuclear magnetic resonance, muon spectroscopy, Mossbauer). In addition, at the end of the course the students are familiar with several magnetic and superconducting materials and with their importance for current research and for technological applications.

Programma/Contenuti

MAGNETISM

-> Introduction:

magnetic moments and quantum mechanics; the coupling of two spins.

-> Isolated magnetic moments:

Hamiltonian of an isolated atom in a magnetic field; Larmor diamagnetism; paramagnetism and Brillouin theory; the Curie law vs. ground state of ions and their fine structure; comparison with experiments and Crystal field contribution; Van Vleck Paramagnetism. Applications of diamagnetic and paramagnetic materials: how to reach very low temperature by using the adiabatic demagnetization. Nuclear spins and hyperfine structure.

-> Ordered and Magnetic structures:

Summary of Interactions (Dipolar, exchange); Ferromagnetism, Antiferromagnetism and Ferrimagnetism: The Weiss model and the quantum origin of the molecular field. Applications of Ferromagnetic materials.

-> Magnetism in metals:

Pauli paramagnetism; Landau levels and Landau diamagnetism.

-> Additionally, brief introduction also to concepts of:

order broken symmetry and phase transitions (Landau theory); excitations and magnons; domain walls and magnetocrystalline anisotropy.

-> Experimental methods to measure magnetic moment and susceptibility of materials.

-> Principle and applications of magnetic resonance techniques:

Nuclear magnetic resonance and Magnetic Resonance Imaging (classical and quantum approach); Electron spin resonance; Mossbauer spectroscopy; Muon spin spectroscopy.

 

SUPERCONDUCTIVITY

-> Introduction of superconductivity: main properties, materials and their characteristic parameters and application.

->Thermodynamic properties of superconductors:

Free Energy and thermodynamic field; entropy and specific heat.

-> Perfect diamagnetism:

The Meissner effect and the magnetic levitation; The London model.

-> Type-I and type-II superconductors: critical magnetic fields vs characteristic parameters.

-> Microscopic description of the superconducting condensate:

Cooper pairs; introduction to BCS model; the superconducting gap; comparison with experiments: isotopic mass effect and different confirmations of the Cooper pairs formation.

-> Quantization of magnetic flux in a superconducting ring.

-> Josephson effects and superconducting quantum interference device. Application of Josephson devices.

-> Ginzburg-Landau theory of superconductivity.

Testi/Bibliografia

1] Lecture notes.

[2] Steve Blundell, Magnetism in Condensed Matter (Oxford University Press).

[3] J. M. D. Coey, Magnetism and Magnetic Materials (Cambridge University Press).

[4] C. Kittel, Introduction to Solid State Physics (John Wiley & Sons 2005).

Metodi didattici

Frontal lectures using the blackboard for the demonstrations and a slide projector for viewgraphs and graphic renderings.

Modalità di verifica dell'apprendimento

Oral examination.

Strumenti a supporto della didattica

Blackboard, overhead projection.

Orario di ricevimento

Consulta il sito web di Samuele Sanna