Jump to content

Talk:Bloch wall

Page contents not supported in other languages.
From Wikipedia, the free encyclopedia

This image is not match descriptive[edit]

what about image and some more description and the link to the other page is missing it looks like there are better sources for the information —Preceding unsigned comment added by 84.109.232.240 (talk) 20:46, 8 July 2008 (UTC)[reply]

Agreed, have no idea what that image is. Needs description or should be removed. —Preceding unsigned comment added by 193.231.19.55 (talk) 10:53, 10 February 2009 (UTC)[reply]

Image has been replaced with a general External Links section, including an animation. William James Croft (talk) 01:10, 16 May 2009 (UTC)[reply]

What is actually described is a Neel wall[edit]

For a Bloch wall, the magnetization rotates *in* the plane of the wall. —Preceding unsigned comment added by 134.34.147.227 (talk) 12:35, 26 February 2009 (UTC)[reply]

Well then, be WP:BOLD and edit! Headbomb {ταλκκοντριβς – WP Physics} 06:41, 5 March 2009 (UTC)[reply]

No, this is not true, a bar magnet has a Bloch wall on the centerline. So this is a THROUGH plane transition. Added some clarification text to the article. William James Croft (talk) 00:57, 16 May 2009 (UTC)[reply]

Quote below is from Van Norstrand's Scientific Encyclopedia, 1958 edition, pages 201 and 202, as follows:

"This is a transition layer between adjacent ferromagnetic domains magnetized in different directions. The wall has a finite thickness of a few hundred lattice constants, as it is energetically preferable for the spin directions to change slowly from one orientation to another, going through the wall rather than to have an abrupt discontinuity". William James Croft (talk) 01:07, 16 May 2009 (UTC)[reply]


PLEASE FIX THIS PROBLEM:

A Bloch wall is a narrow transition region at the boundary between magnetic domains, over which the magnetization changes from its value in one domain to that in the next. The magnetization rotates through the plane of the wall unlike the Néel wall where the magnetization rotates in the plane of the wall. For example, a Bloch wall is formed at the center line of a bar magnet where the domains switch north/south direction. An example of a Néel wall transition is shown in the animation below.

The highlighted sentence is completely wrong and should be removed. There is no Bloch wall in the center line of a bar magnet. There is no Bloch wall at all in a standard bar magnet. This is a pseudoscience concept that follows the statements made by John Bedini. —Preceding unsigned comment added by 69.157.229.234 (talk) 02:17, 23 November 2010 (UTC)[reply]

Some clarifications[edit]

The picture on the right is Néel wall, not Bloch wall: in case of reversely magnetized domains and a wall separating them (the wall is parallel to the magnetization direction) Bloch wall has magnetization parallel to the wall, while Néel wall has magnetization which is perpendicular to the wall at the middle of the wall thickness. On the picture the wall is "horizontal", and at the middle of the wall thickness the magnetization is vertical, as in Néel wall; in a Bloch wall, the magnetization would be perpendicular to the screen there. In other words, in Néel wall the magnetization is everywhere in the plane of the picture, while in Bloch wall it is in the horizontal plane (= plane of the wall; the plane of the picture is vertical when viewed on a screen).

The movie "Néel wall transition animation (but mislabeled as Bloch)" is neither Néel nor Bloch - it just doesn't show any magnetization at the middle of the wall thickness.

"For example, a Bloch wall is formed at the center line of a bar magnet where the domains switch north/south direction" - wrong, there is no significant change of magnetization there. Usually, a magnet contains a lot of Bloch walls, as it contains a lot of magnetic domains, which have at least slightly different direction of their magnetization - and it is mainly result of imperfect magnetization of the magnet. Even if a magnet were magnetized perfectly, so it would be a single domain, such a state would not be stable - at the magnet poles its field diverge, and forces the material to form domains magnetized nearly perpendicularly to the magnetization direction of the magnet. These newly formed domains will be separated from the "main domain" by Bloch walls. On such a wall the magnetization would not reverse its direction: the change of the direction would be less than right angle. The angle between main magnetization direction and the Bloch wall must be such as the angle between the wall and the new domain magnetization direction, because of Bloch wall rules.

Bloch wall rules: magnetization perpendicular to the wall is constant (violation would create inner pole, forbidden for the Bloch wall); if the wall separates two domains is without material change, the magnetization parallel to the wall must have constant value, but its direction changes across the wall (because the material is everywhere fully magnetized).

Contrary, the Néel wall forms inner poles - in a sample of material in the form of a thin layer these inner poles are smaller (as their size is limited by the sample thickness), than external poles from the Bloch wall would be (as the field of these inner poles are parallel to the plane of the layer, while the Bloch wall would have magnetization perpendicular to the layer).

JerzyTarasiuk (talk) 22:28, 22 May 2011 (UTC)[reply]

"The magnetization rotates through the plane of the wall unlike the Néel wall where the magnetization rotates in the plane of the wall" - just reverse, as was explained above.

(I took the Bloch/Néel from the The Neel to Bloch domain wall phase transition in ferromagnetic strips in http://en.wiki.x.io/wiki/N%C3%A9el_wall - hope it is correct)

JerzyTarasiuk (talk) 23:14, 22 May 2011 (UTC)[reply]

Some references I found about distinguishing Bloch/Néel walls; both say the same - Wikipedia exchanged Bloch with Néel:

Figure 1. A Bloch wall and a Néel wall in a thin film. The magnetization in the Bloch wall is normal to the plane of the film. In the Néel wall the magnetization is parallel to the surface.

JerzyTarasiuk (talk) 00:24, 23 May 2011 (UTC)[reply]

JerzyTarasiuk (talk)

Retrieved from "http://en.wiki.x.io/w/index.php?title=Talk:Bloch_wall&oldid=1200188234"