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چکیده
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It is well-known that the cation distribution in cobalt ferrite can be significantly affected by various parameters such as cobalt content, synthesis method, and heat treatment. Heat treatment can be applied either during the synthesis or as a post-synthesis procedure. The temperature dependence of the susceptibility is one of common methods for determining the Curie temperature. In such measurements, in both soft and hard magnetic materials, the initial susceptibility is often seen to exhibit a sharp maximum (known as Hopkinson effect) slightly before the Cuire temperature. However, this peak may be broadened due to non-homogeneity or cation redistribution in the sample. In this work, we synthesized Co0.25Fe0.75Fe2O4 nanoparticles using coprecipitation. Based on the (T) measurement of the as-synthesized sample, a three-hour air annealing was conducted on the sample at different temperatures. Then the samples were allowed to cool down to room temperature. The (T) measurement of the annealed samples indicated magnetic/structural stability. In addition, the room temperature magnetization curves suggested a great potential for controlled tuning of the magnetic properties, i.e. room temperature magnetization, coercivity, and squareness of the sample, using this approach. This control over magnetization and coercivity could be particularly useful in applications such as magnetic hyperthermia, where a high saturation magnetization and a moderate effective anisotropy are advantageous. Moreover, X-ray diffraction analysis showed a considerable enhancement in phase transition of the samples at high temperatures compared to pure magnetite nanoparticles.
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