Polycrystalline Scale Electrodynamics in MM

Among many works on the role of grain boundaries in magnetic materials there are few with the distinctive figures of the volumetric morphology (appearance)

with the detailed microgeometry of such magnetic materials (MM), as studies by Fischer, R. and Kronmuller, H., "The Role of Grain Boundaries in Nanoscaled High-Performance Permanent Magnets," J. Magn. Magn. Mat., Vol. 184, pp. 166-172, 1998a, and Fischer, R. and Kronmuller, H., "Importance of Ideal Grain Boundaries of High Remanent Composite Permanent Magnets," J. Applied Physics, Vol. 83, No. 6, pp. 3271-3275, 1998b.

On the page 3271 of last paper authors wrote - "Within a thin intergranular layer of about 3 nm thickness the material parameters deviate from their initial values. It is well known that near the grain boundaries the atomic lattice deviates from the ideal structure. This should also affect the local material parameters in the continuum theory of micromagnetism."

We would add to this that - a) the grain lattices themselves are never be of the perfect structure - and this means that the lattices are not correct or "perfect" all the time. This drags behind the issue of the lower scale physics into the picture; b) To be seen in the continuum theory of magnetism the features, parameters should be properly (correctly) modeled from the real sub-grain scale of such a heterogeneous medium (here as continuum itself) up to the continuum (experimentally measured, with the fitting scale of measurement) upper heterogeneous scale of those parameters.

The morphology shown and analyzed in these papers can be considered as the one REV for the Upper scale physical matter. It is obvious that these structures are the perfect subject for application of scaled modeling for these two scales of the range 0(1-100) nm at lower scale and of the 0(0.1-1) mkm for the upper scale modeling space.

As one can say that the values of magnetization vector of the lower scale volume ~ 0(1-100) nm are of no interest as to characterize the material of such structure

At the same time the real interest and importance for application present the properties of the characteristic volume of the size of the REV 0(1-10) mkm or even larger. Still, depending on the appllication of interest - that could be the nanoscale or microscale volume of description critical for applications as spintronics or just extended properies hard MM. And all these are the VAT Scaling Modeling field subjects.

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Copyright © 2001...Thursday, 22-Jun-2017 20:24:26 GMT V.S.Travkin, Hierarchical Scaled Physics and Technologies™