Difference between a ferromagnet and a paramagnet?

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Discussion Overview

The discussion centers on the differences between ferromagnets and paramagnets, particularly in the context of magnetic hysteresis. Participants explore definitions, properties, and behaviors of these two types of magnetic materials, as well as implications for presentations and understanding of magnetism in solids.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that ferromagnets are permanent magnets while paramagnets are not, suggesting this as a fundamental distinction.
  • Others challenge the notion that all ferromagnets are permanent magnets, noting that soft ferromagnets have low remanence and do not function well as permanent magnets.
  • One participant describes the behavior of ferromagnets, stating that they contain magnetic dipoles that influence each other, leading to alignment and an enhanced magnetic response.
  • A question is raised regarding the behavior of paramagnets, specifically whether their dipoles are completely random.
  • Another participant introduces a mathematical perspective, indicating that in paramagnets, magnetization (M) is proportional to the applied magnetic field (H) through a positive susceptibility (\chi), while in ferromagnets, M and H are largely unrelated and M is significantly larger than H.
  • There is a suggestion for the original poster to consult additional resources to better understand the basics of magnetism in solids before the presentation.

Areas of Agreement / Disagreement

Participants express differing views on the nature of ferromagnets and paramagnets, particularly regarding the permanence of ferromagnets and the behavior of dipoles in paramagnets. The discussion remains unresolved with multiple competing perspectives presented.

Contextual Notes

Some claims depend on specific definitions of terms like "permanent magnet" and "soft ferromagnet," which may not be universally agreed upon. The mathematical relationship between magnetization and applied field in ferromagnets is also presented without consensus on its implications.

ultimateguy
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I'm doing a presentation on magnetic hysteresis, and I have a feeling one of the profs will ask me what is the difference between a ferromagnet and a paramagnet. I haven't taken my 3rd year E&M class yet, so I would just like to know what I should answer.
 
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Ferromagnets are permanent magnets and paramagnets are not. This is probably the simplest and most important distinction.
 
StatMechGuy said:
Ferromagnets are permanent magnets
Not quite true. A ferromagnet with a large remanence makes a good permanent magnet. A ferromagnet with a small remanence (ie: a soft ferromagnet) does not make a good permanent magnet.
 
Ferromagnets contain magnetic dipoles that 'influence' other dipoles around them, allowing them to align with one another. This property results in an enhanced magnetic response, as there is a reduced random variation in dipole orientation.

Claude.
 
Claude Bile said:
Ferromagnets contain magnetic dipoles that 'influence' other dipoles around them, allowing them to align with one another. This property results in an enhanced magnetic response, as there is a reduced random variation in dipole orientation.

Claude.

And how do paramagnets behave? Are the dipoles just completely random?
 
ultimateguy said:
I'm doing a presentation on magnetic hysteresis, and I have a feeling one of the profs will ask me what is the difference between a ferromagnet and a paramagnet. I haven't taken my 3rd year E&M class yet, so I would just like to know what I should answer.
In a paramagnet, the magnetization (M) is can be given as M=\chi H where
\chi is positive. In a ferromagnet, M and H are almost unrelated, and M is much larger than H in magnitude. The use of \chi in ferromagnetism is meaningless, altough some engineers try to use it.
 
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