Question sessions
The purpose of a research School is to provide young scientists the basics in a working field. With this respect
interactivity between students and lecturers should be promoted. In this respect a key aspect of ESM is the possibility to raise questions during the course of the lectures, interrupting the lecturer. Questions can also be posted anonymously in 'question boxes'. Special sessions for answering these questions are organized, typically 1h every day or two days, during which the lecturers or voluntary students will present in more detail issues raised by the students during the lectures or anonymously through a question-box. Below is a list of questions raised and explained in 2009. Whenever the answer has been supported by slides, these are or will be made available.
- Is it the molecular field that creates the moments, or the moments that create the molecular field?
- Susceptibility as a function of atomic number Z: there is a clear trends among groups of elements. Please discuss.
- What is the physical implication of [s^2,s_z]=0? As an experimentalist how can I be convinced?
- What is the source of spin angular momentum?
- How is it correct to write the hamiltonian of an Ising system?
- The magnetic work is sometimes written as MdH, sometimes HdM. What should one use?
- Why the zero temperature magnetization is in some cases different from the magnetization that you estimate from the Curie constant.
- Discuss dipolar and multipolar expansions in electrostatics versus magnetostatics.
- Why is the singlet state associated to antiferromagnetic coupling and the triplet state to ferromagnetic coupling?
- Assuming we have two ferromagnetic particles with 50microns and 100microns dimensions with same magnetization. Which one has the biggest demagnetizing field?
- Does the magnetism of magnetic oxides depend on the substrate or substrate oxidation?
- What is the Mössbauer spectrum of a particle in the superparamagnetic regime?
- Spin density waves. Where does the spin come from in Cr? Is there also a Charge Density Wave, or is the spin separate from the charge?
- In the case of a Dilute Magnetic System based on a paramagnetic oxide (Ex: Co:ZnO), is the magnetization is localized at the structural defects? Is the interaction between the magnetic moments at the grain boundaries and the 3d moment of dipolar nature?
- Can you explain qualitatively variable range hoping?
- Can you re-explain superexchange?
- Do negative effective masses exist?
- Field-cooled and Zero Field Cooled: how do I know if it is a spin glass or a superparamagnetic system?
- How can I calculate the magnetostatic field from non-spherical particles such as cubes or octahedron? Furthermore, what happens if their magnetization is not homogeneous? [ Answer ]
- Anisotropy energy: Can you demonstrate all the terms of the magnetocrystalline anisotropy, depending on the symmetry? [ Answer ]
- What is the spin-flop transition? [ Answer ]
- Microscopic origin of the quenching of the orbital momentum. [ Answer ]
- Microscopic origin of the Dzialoshinsky-Moriya interaction [ Answer ].
- What is the Fermi liquid model? When is it useful?
- Why domain wall velocity cannot be faster than the sound of speed in some materials? Is this true?
- Why the CIP GMR depends on the mean free path, and the CPP GMR on the spin diffusion length?
- In FC/ZFC, why in some cases the FC curve does not start from zero magnetization, but from a finite value?
- Explain the physical situation of spin injection from a ferromagnetic semiconductor in a non-magnetic semiconductor.
- Why is there no spin splitting in s conduction band of 3d metals, whereas there is in the conduction band of magnetic semiconductors?
- Given the failure of the Stoner model, what is the origin of magnetic ordering in metals?
- Two recent papers have been published recently in Science proving the existence of magnetic monopoles. Please discuss.