Nanowire and thin film magnetisme

[physicist888]

hi there
im searching for an answer about matter magnetism.
actualy, i need to know which energies of anisotropy are so different betwen the bulk and a thin-film .
then i need to know which energy of anisotropy is so different between a nanowire and a thin-film.
10x for your repply

 

[physicist888]

none know about thin-films?

 

[Gokul43201]

The change in anisotropy as a function of thickness has been studied by several groups in different heterostructure systems. There was a talk on this in one of the recent APS March Meetings, but I don't remember anything about it.

 

[f95toli]

Isn't it just due to the "usual" reasons?
I.e. bulk means a 3D system, a thin film (thinner than the relevant length scale, usually some sort of correlation length) a 2D system and in a nanowire a 1D system?
I don't know very much about magnetism, but that is the way it works with e.g. superconductivity.

 

[Gokul43201]

I don't know much eaither - not even enough to know if the "usual" reasons are all there is to it, though I suspect not. With magnetic systems, an important length scale is the size of a magnetic domain. When the sample thickness approaches this value, things begin to change. But in addition, there's all kinds of other effects in low-dimensional systems coming from strain fields, RKKY-like interactions in heterostuctures, possible metal-insulator transitions with changing thickness, possible structural transitions and I imagine, a lowering of the Curie Temperature as you get to fewer and fewer atomic layers in the thin film due to the competition from thermal fluctuations becoming more important - I really don't know anything about these.

The last part is very loose speculation from me - a guess, based on what the Mermin-Wagner theorem has to say about LRO in truly 2D systems. I imagine this should apply to superconductivity as well.

 

[physicist888]

actually there are many type of magnetic anisotropy in a solid. the first is related to the crystal structure of the solid ( hexagonal, tetragonal...etc) and the sort of thi energy is the interaction LS.
the second anisotrpy is due to the interaction betwen the magnetisation and the demagnetisation Field.
the third is the interface anisotropy due to the superposision of many thin-films the one over the other.
the last one ( interfaces) dosent exist in the case of bulk, so its equal zero in the case of bulk.
but, in the case of nanowire, if we would like to compare the different energies between a nanowire and a ultra thin-film, i don't know. infact this is my question...