At 300 K, the nanocrystals become superparamagnetic because of size effects and thermal fluctuations. The inset of Figure 3b reveals the coercivities of all nanocrystals less than 10 Oe. Moreover, the magnetizations of the nanocrystals at 30 kOe are reduced to 30.4 emu/g for Zn ferrite, 37.5 emu/g for Mn-Zn ferrite, and 47.6 emu/g for Mn ferrite, owing to the thermal effects. From the outcomes, it is obvious that the increase of the Mn concentration leads to the VX 809 increase of the magnetization

value. The change in magnetization due to the compositional change may be explained simply by the different moments of the ions, 5 μ B of Mn2+ ions which are higher than 4 μ B of Fe2+ ions, in turn 0 μ B of Zn2+ ions. Other factors such as the inversion parameter in the spinel structure may be considered for comprehensive elaboration Selonsertib of the mechanism. It is useful to remark that the inversion parameter is generally measured by extended X-ray absorption fine structure (EXAFS) analysis or Mössbauer spectroscopy [26, 27]. Figure 3 Magnetic analysis of the ferrite nanocrystals.

(a) M-H hysteresis curves at 5 K and (b) 300 K. Furthermore, the temperature dependence of magnetization was recorded in Figure 4 from 5 to 400 K under the applied magnetic field of 100 Oe by the zero-field-cooling (ZFC) and field-cooling (FC) modes. The M-T curves evidently manifest the superparamagnetic behavior of the ferrite nanocrystals. Overall, the magnetization of the nanocrystals in the FC mode decreases gradually as the temperature increases. In the case of the ZFC mode, the magnetic moment of the nanocrystals is frozen to almost zero at the low temperature.

With the increasing temperature, the magnetization increases until the blocking temperature (T B) then decreases like the FC mode. The measured T B of the ferrite nanocrystals are 80 K for Mn ferrite, 56 K for Mn-Zn ferrite, and 66 K for Zn ferrite, respectively. Figure 4 ZFC-FC curves under the magnetic field of 100 Oe for the ferrite nanocrystals. Conclusions We have synthesized the ferrite nanocrystals which exhibit OSBPL9 high crystallinity and narrow size distributions via the non-aqueous nanoemulsion method and compared three types of samples from Zn ferrite, Mn ferrite, to Mn-Zn ferrites. The structural and chemical measurements performed by XRD and XRF Ivacaftor cell line indicated that the ferrite nanocrystals were successfully produced. All samples behave ferrimagnetically at 5 K and superparamagnetically at 300 K, individually. As the concentration of Mn increases, the magnetization value of the ferrites increases. Furthermore, the M-T curves obtained by the ZFC-FC modes clearly substantiate the superparamagnetism of the ferrite nanocrystals. Acknowledgements This work was supported through the National Research Foundation of Korea which is funded by the Ministry of Science, ICT and Future Planning (NRF-2010-0017950, NRF-2011-0002128). References 1.