• 054347 - MAGNETISM AND SUPERCONDUCTIVITY

The course presents the two most important manifestation of ordering phenomena in solids: magnetism and superconductivity. The two are crucial for the understanding of the transport properties of crystalline materials, and can be exploited in a multitude of applications. Magnetism and superconductivity are governed by microsopic interactions, ultimately among electrons, but the macrosopic phenomenology is the result of interactions and dimensionality.

The objective of the course is thus to provide a broad knowledge and understanding of ordering phenomena in solids. Phenomenology, experimental methods and theoretical models will be considered and confronted, with the aim of broadening the student's knowledge of ordering phenomena in solids and to underline how dimensionality influences them.

Lectures and exercise sessions will allow students to:

• Know the fundamental concepts of ordering phenomena

• Recognise the different types of magnetic order

• Know the general phenomeonology of superconductivity 

• Determine which experimental methods can be used in the study of magnetism and supeconductivity and, in general , of ordering phenomena in solids

• Read and understand original reaserach papers in the fields of magnetism and supeconductivity 

• Present a brief seminar on basic concepts and advanced examples on modern magnetism and superconductivity  

Therefore, after passing the exam, the student will be able to: 

DD1 - Understand the principles of magnetism and order phenomena, know the terminology related to them, employ the basic models applicable to them

DD2 - Recognize analogue of magnetism and superconnductivity in other contexts and apply models ant techniques in new contexts of physics and tecnology

DD4 - Communicate her/his own perception of basic physics phenomena in a formal presentation 

Magnetism of isolated magnetic moments
                  Phenomenology: recalling diamagnetism, paramagnetism.

Atomic moments.
                 Hunds rules
                 Crystal field: origin of CF, quenching of orbital moments, Jahn-Teller effect.

Exchange interaction
                  Examples of simple 3d transition metal oxides (NiO, MnO, Fe3O4)
                  Perovskites
                  Manganites and cuprates

Magnetic order and magnetic structures.
                 Heisenberg and Ising models

Magnetism in metals
                 Pauli paramagnetism
                 Landau diamagnetism 
                 Stoner model 
                 RKKY interaction, Kondo effect

Excitations in magnetic systems 
                 Spin waves
                 Stoner excitations

Magnetism at low dimensionality 
                 Spin chains and spin ladders
                 2 dimensional magnets
                 Thin films

Superconductivity:
                Phenomenology: transport, susceptibility, thermodynamics 
                London equations
                Josephson effect 
                Ginzburg-Landau model 
                BCS theory 
                Cuprate superconductors (also as an example of 2D antiferromagnets).

Experimental techniques.
                Magnetic resonances, Mössbauer spectroscopy, muon spin rotation.
                Elastic and inelastic scattering of neutrons and x-rays for magnetic structure and magnetic excitations.
                Magneto-optical techniques.

General physics (in particular electromagnetism)
Quantum physics
Structure of matter and atomic physics 
Avanced anlaysis and linear algebra
Solid state physics.

The exam consists of two parts held during a single interview, in English.

1) A seminar of 20-25 minutes, on a subject pre-assinged by the teacher. The student has to present the genral concepts of the theme in a correct and complete way, providing some examples at the level of the lectues and of the teext book. The student is also invited to look for original examples, applications, interconnections with other subjects, to demonstrate a higher level of understanding. A powerpoint presentation is best suited for the seminar, but black/white board option is also possible. 

2) Two or three questions on the core of the course as presented in the lectures. The student is requested to answer at the black/white board to show her/his understanding of the basic concepts and notions of the course. Theoretical and experimental aspects will be valued equally important.

A fully successful exam (27-30/30) will be deemed when a solid and broad mastering of the concepts of ordering phenomen in solids is demonstrated.

An average grade (22-26/30) will be the result of failry complete understandig of individual themes but with limited interconnection among subjects.

A pass level (18-21/30) will correspond to a minimum knwleged of individual notions.