# Magnetic Nanoparticles as Mediators for Magnetic Hyperthermia Therapy Applications: A Status Review
## 3 Results and Discussion
### Magnetic Measurements  
Figures 20-24 show the magnetic properties of maghemite MNPs and maghemite MNPs coated with CM-dextran, (Mg, Ti)-ferrite MNPs, as-prepared and thermally homogenized NiCu MNPs (microemulsion technique), NiCu MNPs (sol-gel method), and ball-milled NiCu MNPs. The magnetic properties of the MNPs were investigated using a Lake Shore 7307 vibrating sample magnetometer.  
Figure 20 shows the magnetization vs. the magnetic field of the as-synthesized and CM-dextran-covered maghemite particles [27]. The uncoated particles show no hysteresis and have a saturation magnetization (\(M_{\rm s}\)) of 65.2 emu/g. The magnetization of the coated MNPs was about 55 emu/g, which is lower than that of the uncoated sample. The average particle diameter of our particles determined by magnetic measurements was 8.20 nm (sample A) and 8.17 nm (sample B). Comparing the size with the XRD and the TEM analysis, certain sizes of nanoparticles are slightly smaller in the magnetic measurements, because the so-called \"dead layer\" is not considered in the magnetic measurements.  
Figure 21: Hysteresis for (Mg, Ti)-ferrite as-synthesized (a) and milled (b) powder.  
Figure 22: Magnetization vs. the AMF for the as-prepared and homogenized NiCu MNPs (microemulsion method).  
The magnetization vs. magnetic field curve for the (Mg, Ti)-ferrite particles measured at room temperature under an applied magnetic field of 1 T is shown in Figure 21[26]. The magnetization of the as-prepared samples at 1 T is higher than the magnetization of the milled sample, which is 8 emu/g. This reduction in magnetization due to milling is a well-known phenomenon. It is caused by induced mechanical stresses and an increase in the specific surface area, consequently, an increase in the non-magnetic fraction (\"dead layer\"), which is usually located on the surface of the particles and is the result of imperfect coordination and, finally, a non-collinear spin configuration.  
Figure 22 shows the magnetic measurements indicating that the magnetization is greatly reduced in the stabilized samples [41]. The MNPs in the as-prepared state exhibit \(M_{\mathrm{s}}\)-20 emu/g, while it decreases to \(\sim\)2.5 emu/g in the stabilized MNPs. To obtain homogenized nanoparticles that have a \(T_{\mathrm{C}}\) in the therapeutic range, homogenization is necessary, which of course contributes to the drop in magnetization in homogenized nanoparticles.  
Figure 23 shows the magnetization of the bare A, B, and C MNPs synthesized by a sol-gel method [103]. The magnetization was measured concerning the magnetic field at room temperature. It can be seen from the figure that the magnetizations measured at \(H\) = 10 kOe are good approximations for \(M_{\mathrm{s}}\) since the slopes of the curves are low under the field \(H\) = 6 kOe. The considered samples have a similar size, which shows that the size does not influence the magnetization as much as the influence of the different compositions in the Ni\({}_{1-x}\)Cu\({}_{x}\) alloy. The average particle size determined by magnetic measurements was 15.4 nm (Ni\({}_{67.5}\)Cu\({}_{32.5}\) (A)), 16.4 nm (Ni\({}_{62.5}\)Cu\({}_{37.5}\) (B)), and 17.6 nm (Ni\({}_{60}\)Cu\({}_{40}\) (C)).  
Figure 24 shows the magnetization vs. the magnetic field of the Cu\({}_{1-x}\)Ni\({}_{x}\) alloy particles [55]. The measurements were performed at room temperature and under the influence of an AMF of 10 kOe. The hysteresis loop is not expressed in any sample, indicating the superparamagnetic properties of the Cu\({}_{1-x}\)Ni\({}_{x}\) MNPs prepared by mechanical milling. The \(M_{\mathrm{s}}\) of the samples ranges from 2 to 50 emu/g and depends on the nickel concentration of each sample.