## 3 Results and Discussion
In order to check this conjecture, we repeated our measurements at four different temperatures on the sample used in Experiment 3 in a wide velocity range (Experiment 4) to see all components including the magnetically split one. The resultant spectra confirmed the presence of a sextet (Figure 4). The Mossbauer parameters for this sextet at 90 K were obtained as follows: \(\delta\) = 0.41 mm/s, \(B\) = 42.6 T, \(2\epsilon=-0.04\) mm/s. Evaluating the spectra with a model assuming the regular doublet for ferrate(VI) and a combination of an iron(III) doublet (i.e., that of FeIII(2)) and a sextet, the trends of the line areas as a function of temperature were found to be normal (Figure 4) if the sum of the area of the iron(III) doublet and the sextet was considered as the \"real\" FeIII(2). The evaluated Mossbauer parameters are shown in Table 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \(T\) [K] & **86** & **130** & **160** & **200** \\ \hline \multirow{2}{*}{**Ferrate(VI)**} & \(\delta\) **(mm/s)** & \(-\)0.817 & \(-\)0.831 & \(-\)0.845 & \(-\)0.858 \\ \cline{2-6}  & \(\Delta\) **(mm/s)** & 0.114 & 0.118 & 0.138 & 0.133 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mössbauer parameters found, in Experiment 4, for the ferrate(VI), and the magnetic (sextet) and superparamagnetic (doublet) components of the species FeIII(2) as a function of temperature. Isomer shifts are given relative to \(\alpha\)-Fe at room temperature. Errors are \(\pm 1\) in the last digit. Figure 4: Mössbauer spectra of a ferrate sample containing degradation product FeIII(2) recorded at the indicated temperatures (Experiment 4), and the temperature variation of the normalized areas for ferrate(VI) (purple squares) and FeIII(2) (orange dots), the latter meaning the sum of the areas of the sextet and the iron(III) doublet. In order to reproduce this finding, another ferrate(VI) sample with a larger amount of degradation product FeIII(2) was measured in a wide velocity range at eight different temperatures (Experiment 5). Figure 5 shows sample spectra from this series together with the temperature variation of the spectral areas. It is clearly confirmed that the iron(III) doublet component is only the superparamagnetic part of the FeIII(2) species showing well-resolved magnetically split lines at 90 K. The Mossbauer parameters for this sextet at 90 K were identical to those found in the previous experiment within the experimental error range: \(\delta=0.46\) mm/s, \(B=42.3\) T, \(2\varepsilon=-0.03\) mm/s. Regarding the temperature variations, the spectral area for the FeIII(2) component was calculated as previously: the sum of the area of the iron(III) doublet and the sextet. It is  
Figure 5: Selected Mössbauer spectra of a ferrate(VI) sample with degradation product FeIII(2) recorded in wide velocity range at the indicated temperatures (Experiment 5), and the temperature variation of the normalized areas for ferrate(VI) (purple squares) and FeIII(2) (orange dots), the latter meaning the sum of the areas of the sextet and the iron(III) doublet. again well demonstrated that both the sextet and the doublet can be assigned to FeIII(2) as two forms of a superparamagnetic system. In this experiment, the blocking temperature is estimated (from visual inspection of the spectra) to be around 200 K.  
Let us recall the two cases depicted in Figures 2 and 3 (Experiments 2 and 3). Although the sextet is not seen in the spectra due to the narrow velocity range, it can be concluded from the trend of the area curves that the blocking temperatures were around 180 K in Experiment 2 and certainly over 220 K in Experiment 3 as deduced from the onset of the normal monotonous decrease in the spectral area of the paramagnetic iron(III) doublet. This onset is expected at a temperature where there is no more magnetically split fraction left. The reason for the variation in the blocking temperatures can be the average particle size and the particle size distribution of the oxyhydroxide/hydroxide phase in the actual experiment.