Question sessions

Question sessions

Below is a list of questions raised by the participants of ESM2015, and addressed by the lecturers during the 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. Thus 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 present in more detail issues raised by the students during the lectures or anonymously through a question-box. Questions raised and explained in 2015 are being listed below on a regular basis. See also the questions raised in 2013.

  1. [to M. Coey] You said that E = - m.B . Is this a postulate, or you can demonstrate it?
  2. [to M. Coey] Some authors (in frustration) speak of magnetic monopoles. You said there are non. Could you clarify?
  3. [to M. Coey] Why do you consider that H is more important in condensed matter physics? After all, it is B that appears in the Lorentz force, it is A directly linked to B that appears in the Hamiltonian. Even for spins, the Heisenberg's Hamiltonian implies B and not H.
  4. [A. Kirilyuk] What are intrinsic and extrinsic effects in damping? Could you comment on the effect of eddy currents?
  5. [A. Kirilyuk] Regarding the continuous motion of the breathing fermi surface and relaxation: how is this relaxation accomplished? Where does the energy go to?
  6. [M. Coey] Why do you write some time = = g μB J and sometimes m=g μB [J(J+1)]^(1/2)?
  7. [O. Isnard] it was mentioned that spin and magentic moment vectors point in opposite directions because of the electrons negative charge. If so, how does a neutral particle like neutron have a magnetic moment?
  8. [O. Isnard] As antiferromagnetic materials have no net magnetization, then how do we detect/measure their AFM properties other than doing temperature-dependent measurements by passing through the Néel temperature?
  9. [M. Coey] Provide a simple picture for the Landé factor
  10. [S. Blundell] How to convert magnetization in μB to temperature in Kelvin?
  11. [S. Blundell] I the Heisenberg hamiltonian empirical, or can it be deduced?
  12. [V. Pop] What is the difference between Ţuica, Palincǎ, Rachiu?
  13. [C. Tiusan] Describe extraordinary magnetoresistance versus GMR. Could you comment on advantages / disadvantages and current applications.
  14. [C. Tiusan] Is there an intuitive way to explain the higher values of TMR with respect to GMR?
  15. [C. Tiusan] Could you make a short tutorial on how to read a band diagram?
  16. [M. Chshiev] Could you elaborate a bit more on the difference between spin diffusion equation (eg lecture G. Bauer) and the LLG equation (eg lecture D. Gründler).
  17. [L. Vila] Is there any soft magnetic material with rather high spin diffusion length (low spin resistivity) at room temperature? What about CoNi alloys?
  18. Why can we have different line shapes in FMR measurements? How can change damping in time domain versus frequency domain? How does damping change in continuous films versus patterned structures? How does damping change in case of in-plane versus out-of-plane magnetization?
  19. [L. Vila] What soft magnetic materials are the most suitable for spintronics (based on current knowledge)
  20. Is there a somewhat simple picture of what exactly the Landé factor is, and its origin?
  21. [M. Coey] Is there any way or experiment to proove the link between magnetic moment and angular momentum, especially when they are antiparallel such as for the electron?
  22. [S Blundell] You talked about superexchange in bulk materials, which requires anions. What about thin film structures?
  23. On the poster of the sumemr school both men and women are listed. All the women and none of the men are involved in thin films. i would like to know if these are related and why.
  24. Are Zeeman enenrgy ad mechanical torque to be calculated with H or with B?
  25. How a non-magnetic layer influences the precession and damping in the magnetic layer?
  26. About the Pauli exclusion principle: can we define a repulsive force between fermions? If there is no force, how do these fermions know they need to avoid each other? How is the information transmitted? What is the spatial range of the Pauli exclusion principle?
  27. [L. Vila] Why is the spin hall angle of opposite signe for different heavy metals (eg Pt and W)?
  28. [M. Chshiev] What is the difference between spin transfer torque and spin orbit torque?
  29. [T. Jungwirth] What will look like the LLG equation for antiferromagnets?
  30. [O. Isnard] A lot of people are working with materials but who does measure the magnetic properties? Is there a database where one can find these properties, like there are for crystallographic tables
  31. [L. Vila] Could you comment on the thickness requirements of the e-beam resist for ultimate resolution?
  32. [L. Vila] Spin Hall effect. What is the influence of sample shape?
  33. [M. Chshiev] In which direction does the DMI vector point in a thin-film bilayer? What determines its directions?
  34. [L. Vila] What are the major factors that forbid the deposition of some materials by some deposition techniques?
  35. [L. Vila] Is electron lithography used by the industry?
  36. [L. Vila] What are the disadvantages of ALD?
  37. [S. Blundell] For hamiltonian -JijJiJj, what is the Tc?
  38. [S. Blundell] Entropy is rather easy to define with localized magnetism. How can it be generalized to band magnetism?
  39. [L. Vila] What is the induced moment in Pt from proximity effects, and is the effect different from spin accumulation?
  40. [C. Lacroix] What is the effect of dimensionality on Curie temperature?
  41. [M. Coey] Is there a dependence of exchange 'constant' on external parameters such as magnetic or electric field?
  42. [G. Bauer] What is the meaning of spin accumulation being a tensor?
  43. [G. Bauer] Discuss the errors intentionaly done or not, in the initial Einstein - de Haas experiment.
  44. [D. Gründler] How does a non-magnetic layer affect magnetization precession and damping?
  45. [S. Valenzuela] Can you comment on magnetic / spintronic -based spintronic. What is the status of research? How does it compare with other technologies?