2021 年 29 巻 3 号 p. 532-537
Present status and prospects of magnetic iron oxide nanoparticle (MION) synthesis and their properties for the development of the next generation magnetic fluid suitable for full-scale applications in engineering and medicine are reported. First, the progress in the development of monodispersed size and shape-controlled MION synthesis technology is reported. Then, the nanoscale magnetic properties and flow characteristics investigated using the fine tunned MIONs are reported. From the microscopic and macroscopic structural analysis of the needle-like condensed phase in a magnetic fluid under an external magnetic field, (a) internal spatial order free and (b) chain clustering condensation of small and large particles, respectively, were identified. On the other hand, the estimation of the magnetic anisotropy of individual MIONs was different from the inversely proportional relationship of surface magnetic anisotropy predicted from the size contribution. In the case of particles with isotropic shapes, magnetocrystalline anisotropy plays a significant role in the low-temperature magnetic properties for engineering and medical applications. Finally, based on the above findings, the guidelines for developing next-generation magnetic fluid are proposed.
