Ferromagnetic transition typical cases

If we examine the Mossbauer spectra (Fig. 25) of the PVA-Fe304 nanocomposites described above with 150 wt % concentration of 20-nm filler particles, we can see that following a decrease in temperature from 290 K (A) to 200 K (B) and then to 77 K (C) the badly resolved doublet, typical for the superparamagnetic state, is substituted by a well-resolved sextet which is evidence for the ferromagnetic state of the system. Such behavior is typical for the super-paramagnetic-ferromagnetic transition which takes place in this case at a temperature of approx. 200 K, at which the intensity of the doublet and the sextet are of the same order. 

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