Talk:Allotropes of iron

Observation of antiferromagnetism in epsilon-iron

The last sentence stating that antiferromagnetism is observed when alloyed cites a purely theoretical paper, therefore the word "observed" is wrong. — Preceding unsigned comment added by 138.51.12.198 (talk) 19:38, 29 August 2019 (UTC)

Ferrite, austenite and iron

Alpha-iron and alpha-ferrite, gamma-iron and austenite, delta-iron and delta-ferrite are not synonymous!!! I corrected the wrong sentences in the text, be careful about it. --Aushulz (talk) 14:02, 11 September 2010 (UTC)

I agree with you on gamma iron and austenite. Austenite almost always refers to the solid solution of gamma iron and carbon, which has different properties than gamma iron alone. However, with the rest, the differences between the terms is somewhat archaic. In modern terminology, alpha iron and alpha ferrite are the same. In older terminology, (late 1800s to early 1900s), alpha ferrite was considered a pure allotrope of iron, whereas alpha iron was supposedly a solid solution of alpha ferrite and carbon, also called troostite (another archaic term). The same with beta iron and beta ferrite, except the solid solution of beta ferrite and carbon was called either beta iron or martensite. Nowadays, ferrite and iron are used almost synonynously, and the metastable "solution" (whether in beta or alpha) is called martensite. But the distinction between gamma iron (gamma ferrite) and austenite remains. Zaereth (talk) 21:10, 20 June 2012 (UTC)

Alpha iron:it occurs from normal temperature to 912 degree centigrade and has a body cubic (b.c.c)lattice crystals. Gamma iron:This occur from 912degree centigrade to 1400degree centigrade and has a crystal structure of face centered cubic(F.C.C)lattice. Delta iron:This occurs from 1400degree centigrade to 1539degree centigrade(molten state)and has a crystal structure of body centered lattice(b.b.c ) Blissoutcatalog (talk) 01:14, 19 April 2019 (UTC)

Inner core structure

It says that at the inner core conditions iron is believed to be in the hcp structure and gives only one scientific reference for this, from 1995. I am not really from the field, and it could be that I do not see the whole spectrum of current thought, but to me it seems as if in recent times the consensus goes more into bcc, see, e.g. L Vocadlo et al., Nature 424, 536 (2003), AB Belonoshko et al., Nature 424, 1032 (2003) and W Luo et al., PNAS 107, 9962 (2010), and that bcc is even favoured by the alloying of light elements, expected to be S and Si. Seattle Jörg (talk) 14:41, 25 March 2013 (UTC)

I don't have much knowledge of the lattice arrangement of solid iron in the Earth's core, but this article is woefully lacking in information about it. Keep in mind that it is theoretical, and the various theories should be explored. This article could really use more in-depth analysis, and perhaps an entire section about it. If you have any information to add, and reliable sources that you can cite, then your help would be appreciated. Zaereth (talk) 00:55, 28 March 2013 (UTC)

Consistency & Curie

The previous paragraph gives a different set of values: 'Curie temperature of 771 °C (1044K or 1420 °F)" It's only one degree but every mention of the curie temp should have the same value. Michael McGinnis (talk) 03:31, 30 December 2016 (UTC)

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Magnetism

There are a few issues here: first, "the random thermal agitation of the atoms exceeds the oriented magnetic moment of the unpaired electron spins and it becomes paramagnetic" is nonsense -- I can understand "random thermal agitation of the atoms" only as their typical thermal displacements as distances on the order of tenths of Angströms, so these don't even have the same dimensions. The thermal displacements have nothing to do with the magnetic transition, and also the size of the ordered magnetic moment has no direct effect -- Co has a much smaller moment but a higher transition temperature. It's just that with increasing temperature, you have more and more excitations of the magnetic moments, and at some point you lose the long-range correlation, which constitutes the phase transition.

Further, strictly speaking beta-iron is structurally different: beta-iron is really cubic, while alpha-iron is not -- even though the effect is not large with such a comparatively light atom, there is some spin-orbit coupling, so that ordered magnetic moments lead to a structural change known as magnetostriction. Bcc Fe has <100> as easy axes, so alpha-Fe is actually tetragonal. It definitely is a different phase.

And finally, it seems that previously the phases were presented sorted by decreasing temperature. At some point, this was turned around, but then you cannot introduce by "As the iron cools further to..." and so on. I will do this change presently. Seattle Jörg (talk) 20:59, 25 April 2021 (UTC)

In my edit just now I adressed all the points listed above -- the prose could still do with some polishing, but at least the contents should now be factually correct. Seattle Jörg (talk) 21:18, 25 April 2021 (UTC)