Evidence on Room-Temperature Magnetic Enhancement due to site-selective charge transfer in Carbon Encapsulated Magnetite nanoparticles
吳文斌2*, 陳啟亮2, 李建興1, 許華書1, Jiunn Chen1
1應用物理系, 屏東大學, 屏東, Taiwan
2國家同步輻射研究中心, 國家同步輻射研究中心, 新竹, Taiwan
* Presenter:吳文斌, email:frankwu@nsrrc.org.tw
We have synthesized the magnetite nanoparticle (Fe3O4 NPs) encapsulated with amorphous Carbon (a-C) that show significantly enhanced almost 20% the room-temperature ferrimagnetism as compared to the pristine Fe3O4 NPs. From the characterization of optical magnetic circular dichroism (OMCD) and soft x-ray spectroscopy (XAS), a strong interfacial interaction in the Fe3O4@a-C nanocomposite have been observed. DFT calculations suggest this interaction is link with uncompensated polarized electronic state contributed from opposite spin orientation of crystallographic site of Fe3O4 in the vicinity of the EF, concluding the electron effect within t2(g) band is crucial for the observation of chemical potential shift of the A-site in Fe3O4 in the x-ray magnetic circular dichroism (XMCD); explaining the microscopic origins for this room temperature magnetic enhancement. In addition, we also report the OMCD imprints the electronic difference between Fe3O4 and γ-Fe2O3. This result is important for the technique serving as in line inspect tool in distinguishing among them.  

Keywords: magnetite, nanoparticle, magnetic enhancement, magnetic circular dichroism, first principle calculation