Hi,Is it fair to say that magnetism rises from the fact that there

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    Magnetism
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Discussion Overview

The discussion centers around the nature of magnetism, particularly in relation to electron spin, the Fermi level, and the role of electronic correlation. Participants explore concepts related to ferromagnetism, antiferromagnetism, and the conditions under which magnetism may arise in materials.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether magnetism can be attributed to an imbalance of up and down electrons and the significance of the Fermi level in this context.
  • Another participant suggests that an imbalance between up and down spin electrons is necessary, but notes exceptions in cases like transition metal compounds where the d-levels may not contribute to magnetism at the Fermi level.
  • It is proposed that having an odd number of electrons does not guarantee ferromagnetism, as the magnetic behavior depends on the exchange interactions among localized magnetic moments.
  • One participant introduces the idea that magnetism often arises from strong electronic correlation, complicating the definition of Fermi energy.
  • A request for clarification on the relationship between electronic correlation, Fermi energy, and the localization or delocalization of electrons in relation to magnetism is made.

Areas of Agreement / Disagreement

Participants express differing views on the conditions necessary for magnetism, particularly regarding the role of electron spin, the Fermi level, and the implications of electronic correlation. The discussion remains unresolved with multiple competing perspectives presented.

Contextual Notes

There are limitations regarding the assumptions made about electron configurations, the definitions of magnetism, and the specific conditions under which different magnetic behaviors manifest. The relationship between localization/delocalization of electrons and magnetism is also not fully explored.

marie2010
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hi,
Is it fair to say that magnetism rises from the fact that there are more up than down electrons or they also have to be at the Fermi level? I am a little bit confused about this Fermi level thing. I heard people saying that up/down electrons difference must be at the fermi level.
Also, does it mean that an odd number of electrons will always give magnetism?
Can someone comment on this, please?
Thanks.
 
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There should be an imbalance between the electrons with up and down spin. All the core levels are generally occupied, hence the imbalance is visible at the Fermi level. However, this may not be true in certain cases. For e.g. in transition metal compounds, if the partially filled d-levels of the transition metal lie below the Fermi level, then you may not see any exchange splitting at the Fermi level and the material can still be magnetic.

Odd no. of electrons may not always show magnetism, if by magnetism you mean ferromagnetism. Ferro- or antiferro-magnetism depends upon the exchange interaction among the localized magnetic moments. Lack of exchange interaction among the localized magnetic moments leads to the paramagnetic behavior.
 


Also mind that magnetism is usually an effect due to strong electronic correlation. However, once electronic correlation is present, it may not even be possible to define the Fermi energy.
 


Thank you all for replying. DrDu, would you please elaborate a bit more about the electronic correlation and the Fermi energy.

Also, could you please help me understand how localization or delocalization of electrons is related to magnetism. Can delocalized charge lead to magnetism?
Thank you.
 

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