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Author Topic: Does Temperature Affect magnetism ?  (Read 7845 times)

Offline neilep

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Does Temperature Affect magnetism ?
« on: 23/09/2007 17:26:31 »
Dear Magnet Magnates (Notice the play on words there ?..eh ? eh ?...sheesh !!..I'm wasted here !)

Here are some nice Magnets :



Nice aren't they ?.Notice how heart shaped and "attractive" they are ?


........just curious...if I heated a magnet up to 100c..would it become less or more magnetic ?..or should I say would the force increase or decrease ?..or neither ?

What about if I dropped the temperature and whammed it in the freezer for a while /..would that affect it ?..if so...why so ?



Hugs and shmishes

neil

mwah mwah mwah !!



 

another_someone

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Does Temperature Affect magnetism ?
« Reply #1 on: 23/09/2007 18:24:45 »
I wish I were a magnate, of anything :)

If you raise the temperature of a magnet above its curie temperature, it will lose its magnetism altogether (there may be a grey area around the curie temperature, but there is no progressive proportionality between temperature and magnetism).

Cooling a magnet that is already well below its curie temperature should have no effect on its magnetism (excepting when you get to the regions of superconductivity).
 

Offline neilep

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Does Temperature Affect magnetism ?
« Reply #2 on: 23/09/2007 18:44:25 »
I wish I were a magnate, of anything :)

If you raise the temperature of a magnet above its curie temperature, it will lose its magnetism altogether (there may be a grey area around the curie temperature, but there is no progressive proportionality between temperature and magnetism).

Cooling a magnet that is already well below its curie temperature should have no effect on its magnetism (excepting when you get to the regions of superconductivity).

Thank Ewe George...I too wish ewe be a magnate....but..if ewe were there's no way you'd be here eh ?

What is the " Curie Temperature ?"

Thanks George...muchly !
 

Offline sohail

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Does Temperature Affect magnetism ?
« Reply #3 on: 23/09/2007 18:49:41 »
And what happens when you get to the realms of superconductivity?
 

another_someone

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Does Temperature Affect magnetism ?
« Reply #4 on: 23/09/2007 19:04:15 »
What is the " Curie Temperature ?"

Depends on the material - each substance has a different curie temperature.
 

another_someone

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Does Temperature Affect magnetism ?
« Reply #5 on: 23/09/2007 19:16:27 »
And what happens when you get to the realms of superconductivity?

http://en.wikipedia.org/wiki/Diamagnetic
Quote
All materials show a diamagnetic response in an applied magnetic field; however for materials which show some other form of magnetism (such as ferromagnetism or paramagnetism), the diamagnetism is completely overpowered. Substances which only, or mostly, display diamagnetic behaviour are termed diamagnetic materials, or diamagnets. Materials that are said to be diamagnetic are those which are usually considered by non-physicists as "non magnetic", and include water, DNA, most organic compounds such as petroleum and some plastics, and many metals such as mercury, gold and bismuth.

Superconductors may be considered to be perfect diamagnets (\ \chi_{v} = −1), since they expel all field from their interior due to the Meissner effect.

http://en.wikipedia.org/wiki/Meissner_effect
Quote
In Physics, the Meissner effect (or Meissner-Ochsenfeld effect) is the expulsion of a magnetic field from a superconductor. The phenomenon was discovered by Walther Meissner and Robert Ochsenfeld in 1933 by measuring the flux distribution outside of tin and lead specimens as they were cooled below their transition temperature in the presence of a magnetic field. They found that below the superconducting transition temperature that the specimens became perfectly diamagnetic, cancelling all flux inside. The experiment demonstrated for the first time that superconductors were more than just perfect conductors and provided a uniquely defining property of the superconducting state.

http://nostalgia.wikipedia.org/wiki/Diamagnetism
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Diamagnetism is a very weak form of magnetism that is only exhibited in the presence of an external magnetic field. It is the result of changes in the orbital motion of electrons due to the applied magnetic field. The induced magnetic moment is very small and in a direction opposite to that of the applied field. When placed between the poles of a strong electromagnet, diamagnetic materials are attracted towards regions where the magnetic field is weak. Diamagnetism is found in all materials, however because it is so weak it can only be observed in the absence of other forms of magnetism.

An exception to the "weak" nature of diamagnetism occurs with the rather large number of materials that become superconducting, something that usually happens at lowered temperatures. Superconductors are perfect diamagnets and when placed in an external magnetic field expel the field lines from their interiors (depending on field intensity and temperature). Superconductors also have zero electrical resistance, a consequence of their diamagnetism. Superconducting structures have been known to tear themselves apart with astonishing force in their attempt to escape an external field. Superconducting magnets are the major component of most MRI systems, perhaps the only important application of diamagnetism.
 

Offline neilep

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Does Temperature Affect magnetism ?
« Reply #6 on: 23/09/2007 19:16:55 »
What is the " Curie Temperature ?"



Depends on the material - each substance has a different curie temperature.

Thanks George...but I meant 'fundamentally' what is the Curie Temperature !! ?...something to do with Madam Curie yes ?
 

another_someone

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Does Temperature Affect magnetism ?
« Reply #7 on: 23/09/2007 19:41:12 »
Thanks George...but I meant 'fundamentally' what is the Curie Temperature !! ?...something to do with Madam Curie yes ?

http://en.wikipedia.org/wiki/Curie_temperature
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named after Pierre Curie (1859-1906)

http://en.wikipedia.org/wiki/Curie_temperature
Quote
The Curie point of a ferromagnetic material is the temperature above which it loses its characteristic ferromagnetic ability. At temperatures below the Curie point the magnetic moments are partially aligned within magnetic domains in ferromagnetic materials. As the temperature is increased from below the Curie point, thermal fluctuations increasingly destroy this alignment, until the net magnetization becomes zero at and above the Curie point. Above the Curie point, the material is purely paramagnetic.

At temperatures below the Curie point, an applied magnetic field has a paramagnetic effect on the magnetization, but the combination of paramagnetism with ferromagnetism leads to the magnetization following a hysteresis curve with the applied field strength. The destruction of magnetization at the Curie temperature is a second-order phase transition and a critical point where the magnetic susceptibility is theoretically infinite.

Essentially, it is just a temperature above which a ferromagnetic material will forget its past magnetic memory (when it is cooled again, it will remember the magnetic environment in which it has been cooled rather than the magnetic memory it had before it was heated).

http://en.wikipedia.org/wiki/Ferromagnetism
Quote
MaterialCurie
temp. (K)
Co1388
Fe1043
FeOFe2O3*858
NiOFe2O3*858
CuOFe2O3*728
MgOFe2O3*713
MnBi630
Ni627
MnSb587
MnOFe2O3*573
Y3Fe5O12*560
CrO2386
MnAs318
Gd292
Dy88
EuO69
« Last Edit: 23/09/2007 19:49:56 by another_someone »
 

Offline syhprum

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Does Temperature Affect magnetism ?
« Reply #8 on: 23/09/2007 20:49:21 »
diamagnetic are those which are usually considered by non-physicists as "non magnetic", and include water, DNA, most organic compounds such as petroleum and some plastics, and many metals such as mercury, gold and bismuth.

Here is a diamagnetic organic compound being levitated in a 10 Telsa field
 
 

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Does Temperature Affect magnetism ?
« Reply #8 on: 23/09/2007 20:49:21 »

 

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