Domain Wall (magnetism) - Magnetism


In magnetism, a domain wall is an interface separating magnetic domains. It is a transition between different magnetic moments and usually undergoes an angular displacement of 90° or 180°. Domain wall is a gradual reorientation of individual moments across a finite distance. The domain wall thickness depends on the anisotropy of the material, but on average spans across around 100–150 atoms.

The energy of a domain wall is simply the difference between the magnetic moments before and after the domain wall was created. This value is usually expressed as energy per unit wall area.

The width of the domain wall varies due to the two opposing energies that create it: the magnetocrystalline anisotropy energy and the exchange energy, both of which tend to be as low as possible so as to be in a more favorable energetic state. The anisotropy energy is lowest when the individual magnetic moments are aligned with the crystal lattice axes thus reducing the width of the domain wall. Conversely, the exchange energy is reduced when the magnetic moments are aligned parallel to each other and thus makes the wall thicker, due to the repulsion between them (where anti-parallel alignment would bring them closer, working to reduce the wall thickness). In the end an equilibrium is reached between the two and the domain wall's width is set as such.

An ideal domain wall would be fully independent of position, but the structures are not ideal and so get stuck on inclusion sites within the medium, also known as crystallographic defects. These include missing or different (foreign) atoms, oxides, insulators and even stresses within the crystal. This prevents the formation of domain walls and also inhibits their propagation through the medium. Thus a greater applied magnetic field is required to overcome these sites.

Note that the magnetic domain walls are exact solutions to classical nonlinear equations of magnets (Landau–Lifshitz_model, nonlinear Schrodinger equation and so on).

Read more about this topic:  Domain Wall (magnetism)

Other articles related to "magnetism":

A Tale Of The Ragged Mountains - Themes - Mesmerism
... can induce a hypnotic state in a patient by the exercise of a force called animal magnetism ... their nervous systems with “animal magnetism”, rays of a universal cosmic fluid ... Mesmerism, which informed him that one human being could control animal magnetism, channel it through space into the nervous system of another human being, and thereby dominate his ideas ...
... In contrast, organisms' use of magnetism in navigation is magnetoception and the study of the magnetic fields' effects on organisms is magnetobiology ... to include magnetobiology, further encompassing almost any combination of the words magnetism, cosmology, and biology, i.e ... years ago, linked to the expression "animal magnetism." The present scientific definition took form in the 1970s, when an increasing number of researchers began to measure the magnetic fields produced by the human body ...
Classical Electromagnetism And Special Relativity - Relationship Between Electricity and Magnetism - Deriving Magnetism From Electrostatics
... is viewed as an effect of electrostatics or magnetism ... Authors usually derive magnetism from electrostatics when special relativity and charge invariance are taken into account ...
Chromium Nitride - Magnetism
... In particular, the importance of magnetism in both the low temperature and the high temperature phases has been demonstrated by means of quantum mechanical calculations of the electronic structure of the ...