What Causes Iron to Exhibit Magnetic Behavior?

[ballballisicious]

URGENT! about iron and magnetism

can u explain briefly the magnetism of iron? i know that some iron ore--haematite and magnetite r called natural iron, but what contribute to the magnetic behaviour of iron?

and, what r the application of iron? all i could find from the internet only gives a general idea about that-- iron is used for constructing bridges, making alloy and kitchen untensils, cutley. r there any application that is more worth-talking? that i can relate it to the internal structure of iron?

any help will be appreciated

 

[tfleming]

http://www.external.ameslab.gov/news/Inquiry/spring96/spin.html

But perhaps the best description of the new formulation's significance is the one given by Katsnelson. "I like to compare the problem of the magnetism of iron to the famous phenomenon of superconductivity," he says. For about 40 years after the discovery of superconductivity, there was no reasonable explanation for it. But once Cooper came up with a mechanism, a very satisfactory theory quickly took shape. The reason, from a technical point of view, is that superconductivity is based on long-range interactions, and you could use a technique called the mean-field approximation to study it. In effect, this approximation reduces a many-body problem to an equivalent single-body problem. So in the case of superconductivity, it was extremely difficult to find the basic idea, but once that idea was found, further steps were not very difficult.

"The magnetism of iron is just the opposite," Katsnelson continues. "The principal idea is well known. It is the exchange interaction between atoms, proposed by Werner Heisenberg and Jacob Frenkel in the 1920s. But because the exchange interactions that underlie magnetism are short-range interactions, we have no satisfactory approximation like the mean-field approximation. And so magnetism is really a many-body problem, and all many-body problems are very difficult.

"Probably not all physicists would agree," he says laughing, "but I believe that one test of our understanding of the many-body problem is the level of our understanding of the magnetism of iron. And that is why I believe all the progress in this problem will be very exciting and very important from a conceptual point of view."

hope this helps!

 

[ZapperZ]

can u explain briefly the magnetism of iron? i know that some iron ore--haematite and magnetite r called natural iron, but what contribute to the magnetic behaviour of iron?

and, what r the application of iron? all i could find from the internet only gives a general idea about that-- iron is used for constructing bridges, making alloy and kitchen untensils, cutley. r there any application that is more worth-talking? that i can relate it to the internal structure of iron?

Your question contains two unrelatied issues - the magnetism of iron, and the uses of iron. That last part, I'll let the engineers on here (especially those civil and mechanical engineers) give you the tons and tons of examples that use iron (including steel).

The question of its magnetism is essentially a question on the origin of ferromagtism (a thread like this in another section of PF has address the many-body issues with ferromagnetism and paramagnetism). The origin of any magnetic properties, be it ferromagnetism, paramagnetism, antiferromagnetism, etc. starts from unpaired electrons in the valence shell. This creates a net magnetic moment for each atom. It is how these individual magnetic moment interacts with each other in a solid that causes it to be all the different 'ism's that I described above. The magnetic moment for iron has a tendency to be alligned with each other over quite a long range, and so this is what creates the ferromagnetic property.

http://hyperphysics.phy-astr.gsu.edu/hbase/solids/ferro.html

Zz.

 

[tfleming]

one way to understand how the magentic domains etc might (for example) become 'fixed' at some previous time, is, that a lattice of atoms cools from hot to cold AND the external magnetic field changes. i.e. magnetic changes in the Earth's geomagnetism (geomagnetic field GMF) after this occurs. So when the magnetic field was 'born' the atoms may well have been in equilibrium with the GMF but later when the GMF has altered or even flipped, the magnetite is no longer in equilibrium and a resultant magnetic field is detected.