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The magnetic modification of vermiculite (MVer) has contributed to an increase in relative area of magnetic component to 9.8% at RT and to 18.2% at 7 K.
Similar to the MVer sample, the assignment of obtained values of the hyperfine parameters accurately to the specific iron oxide or oxyhydroxide is again difficult and not unique.
Moreover, the particles in MMt are not agglomerated as it is at modified vermiculite, and therefore, the MVer sample embodies higher coercivity and remnant magnetization.
The Curie temperature [T.sub.C3]~820 K for MVer and MMt samples corresponds to a ferromagnetic-paramagnetic transition of maghemite, [gamma]-[Fe.sub.2][O.sub.3],  and thereby supports the Mossbauer results.
The behaviour of all samples below RT is documented by the FC/ZFC curves and hysteresis loops at 2 K shown in Figure 11 (Ver, Mt) and Figure 12 (MVer, MMt).
The magnetically modified montmorillonite (MMt) exhibits contrary to the MVer sample superparamagnetic behaviour at RT with nearly zero coercive field and remnant magnetization.
Caption: Figure 6: TEM micrographs of the original (Ver, Mt) and magnetically modified (MVer, MMt) clay minerals.
Caption: Figure 7: Room temperature reflection X-ray powder diffraction patterns of vermiculite (a) and montmorillonite (b) in the original (Ver, Mt) and magnetically modified (MVer, MMt) states.
Caption: Figure 8: Mossbauer spectra of the original (Ver, Mt) and magnetically modified (MVer, MMt) vermiculite (a) and montmorillonite (b) samples measured at room and low temperatures.
Caption: Figure 9: Room temperature magnetization curves of original samples (a), magnetically modified samples (b), and Henkel plots of MVer and MMt samples (c).
Caption: Figure 10: Thermomagnetic curves of the original (Ver, Mt) (a) and magnetically modified (MVer, MMt) samples (b) measured in an external magnetic field of 8 kA/m.
Caption: Figure 12: Low-temperature magnetic properties of magnetically modified (MVer, MMt) samples.
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