what are the factors which can affect the saturation magnetization . and how can we study these factors i.e. how can we conform which factor is playing role.
i am listing some factors which can affect the Saturation magetization of magnetic nanoparticles. please share if you know more and the way of identification.
thanks
a) The disordered surface spins. (How to conform this contribution?)
b) in spherical NP Ms is less (upto 40% less)
c) heating rate is one of the most important parameters that can effectively increase or decrease the saturation magnetization.
d) In magnetic oxides ,There is a large reduction in saturation magnetization which arises due to the weakening of superexchange interaction as a result of missing oxygen bonds.
can stress or slip defects change Saturation Magnetization ??
or any other factor ?
Thanks S.N. Piramanayagam Sir ,
As ive already mentioned Nanoparticles in my question , i havent done this much big mistake.
Ive considered shape (surface and volume) anisotropy energy terms and even in nano size there is a large difference in Ms b/w Spherical and cubical nanoparticles of same dimension.
..
Thanks for your suggestion. Please let me come to know if other factors are also there.
To find the contribution due to disorder of spins on surface ESR, Mossubauer are good methods. While preparation by chemical precipitation method pH is also a factor one needs to be considerd.
I think that the contribution of (d) factor - the weakening of superexchange interaction as a result of missing oxygen bonds - could be checked by annealing of a smaple in oxigen
Dear colleagues ,
if I may contribute to your answer, i would say that important parameters highly related to saturation magnetization (Ms) values in magnetic nanoparticle dispersions are:
- aggregation state or nanoparticle concentration (since intra- e inter-aggregate dipolar interactions would influence Ms values)
- crystalline structure (highly related to chemical composition but also to nanoparticle growth procedure; ie. surface defects)
- magnetic anisotropy (related to chemical composition, crystalline features and nanoparticle morphology)
Concerning to particle size, we have recently shown (G. Salas et al. J. Phys. Chem C 2014) that there is not variation of Ms with size for maghemite NP in the range from 7 to 22 nm when particles are crystalline (thanks to the growth by thermal decomposition). Such preparation method highly reduces surface defects (more pronounced in small NP size).
i hope this may result of your interest
I hope some ideas that we discussed in following paper will be useful concerning to you question
Article Spherical magnetic nanoparticles fabricated by laser target ...
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