## 3 Results and Discussion
### Characteristics of MFP-Processed Samples
#### 3.2.2 Magnetic Properties of MPF-Processed Samples  
Figure 10a-c show the demagnetization (second quadrant of 4\(\pi\)M-\(H\) and \(B\)-\(H\)) curves and plots of \(B\) vs. \((BH)_{max}\) for Sr\({}_{1-x}\)La\({}_{x}\)Fe\({}_{12-x}\)Co\({}_{x}\)O\({}_{19}\) samples (\(x=0.0\), 0.15, 0.2, and 0.3) processed with and without MFP process and sintered at 1230 \({}^{\circ}\)C for 2 h. Here, the direction in which the magnetic field is applied during the \(B\)-\(H\) measurement coincides with the applied field direction during MFP. The 4\(\pi\)M\({}_{r}\), \(H_{ci}\), and \((BH)_{max}\) values for these samples are listed in Table 4. Squareness, Q, is defined by Q = \(H_{k}/H_{ci}\), where \(H_{k}\) is the knee field corresponding to a magnetization of 90% of \(B_{r}\). As shown in Table 4, the highest induction  
Figure 9: The average grain sizes of the Sr\({}_{1-x}\)La\({}_{x}\)Fe\({}_{12-x}\)Co\({}_{x}\)O\({}_{19}\) (\(x=0.0\), 0.15, 0.2, and 0.3) sample sintered at 1230 \({}^{\circ}\)C. The average length of the hexagonal plate (\(d_{avg}\)) (**a**), the average thicknesses of the hexagonal plate (\(t_{avg}\)) (**b**), average aspect ratios (**c**), and average grain volumes (**d**) were separately evaluated from the micrographs shown in Figures 4 and 7.  
remanence (\(B_{r}\) or \(4\pi M_{r}\)) and the largest (\(BH\))\({}_{max}\) of 4.05 G and 3.62 MGOe, respectively, are obtainable from the MFP sample of \(x=0.15\). The increase in \(H_{ci}\) for MFP samples listed in Table 4 is primarily influenced by the increase in \(H_{d}\) listed in Table 2, according to Equation (5). While the increment in \(H_{d}\) from \(x=0.2\) to 0.3 is about twice as much as that from \(x=0.0\) to 0.15, the increment in \(H_{ci}\) for MFP samples is reduced by about 0.76. Therefore, it is difficult to explain the variation in \(H_{ci}\) solely by the variation in \(H_{d}\). According to Equation (5), \(H_{ci}\) is dependent on the magnetic properties, such as \(H_{a}\), \(M_{s}\), and \(M_{r}\), as well as the microstructure factors of \(\alpha\) and \(N\). Meanwhile, the MFP process can largely enhance the grain alignment, and thereby \(M_{r}\) is abruptly increased, which may cause a significant decrease in \(H_{ci}\), according to Equation (5) for a given composition, \(x\). Interestingly, however, after MFP, the \(4\pi M_{r}\)(or \(B_{r}\)) values increase from \(x=0.0\) to 0.15 and then decrease to \(x=0.3\), while \(H_{ci}\) continuously increases with the increasing \(x\), suggesting that the \(4\pi M_{r}\) increase is not always accompanied by an \(H_{ci}\) decrease for different \(x\) values. Furthermore, as shown in Figure 9, after MFP, the increase in aspect ratio with \(x\) leads to an increase in \(N\) and decrease in \(\alpha\), which is presumably responsible for the additional reducing effect on \(H_{ci}\). Consequently, since the increasing effect of \(H_{a}\) is dominant compared with the decreasing effects of \(M_{r}\) and the microstructure factors \(\alpha\) and \(N\), \(H_{ci}\) is considered to increase with the increasing \(x\) for MFP samples. Figure 11 shows the \(H_{ci}\) values versus \(x\) in (a) and also versus \(4\pi M_{r}\) in (b) for Sr1\({}_{-x}\)La\({}_{x}\)Fe12\({}_{-x}\)Co\({}_{2}\)O\({}_{19}\) samples (\(x\) = 0.0, 0.15, 0.2, and 0.3) with and without the MFP process. As shown in Figure 11a, \(H_{ci}\) increases from 3.14 to 3.84 kOe in the MFP samples with increasing \(x\) from 0.0 to 0.3. This increasing tendency of \(H_{ci}\) with \(x\) is also commonly observed for non-MFP samples in this figure. However, the \(H_{ci}\) values for a given \(x\) decrease with increasing grain alignment. The \(w(00l)\) values for non-MFP2 samples evaluated by Equation (6) were 33.4, 35.3, 33.9, and 41.2% for \(x\) = 0.0, 0.15, 0.20, and 0.30, respectively, while those could not be evaluated for non-MFP1 samples. Somewhat enhanced grain alignments for non-MFP2 samples might be induced by the higher pressure of the CIP.