主讲简介:Mogens Christensen,丹麦奥胡斯大学化学系,交叉学科纳米中心,材料晶体学中心教授,主要研究领域包括磁性材料、热电材料、非弹性中子散射、纳米颗粒原位生长研究等。迄今在Nature Materials,JACS,Adv. Mater.等杂志上发表学术论文87篇,在国际、国内会议上作报告和邀请报告81次。Mogens Christensen教授还是晶体学领域的专家,在为改进材料结构表征方面做出了很多贡献,目前在为欧洲散裂源中心(ESS,世界最大中子研究设备中心)主导设计其中的一些设备。
主讲内容:Magnetic materials are the foundation for plethora scientific and technological applications.1, 2 Nano-structuring of conventional magnetic materials has the potential to significantly improve performance and making these useful in a number of applications.3 A promising candidate is the strontium hexaferrite SrFe12O19, due to its pronounced magnetocrystalline anisotropy. By controlling the size of SrFe12O19 nanoparticles, it is possible to tailor the magnetic properties. Control over the size has been achieved by varying synthesis parameters, such as pH, temperature and the metal concentration upon addition of the base. The resulting particles are shown to have a plate-like shape, where the dimensions are thin along the crystallographic c-axis (∼3-8 nm), and large in the ab-plane (∼20-60 nm). The results have been obtained from Rietveld refinement of powder X-ray diffraction data, TEM and AFM. Compaction of the tailored nanoplatelets into bulk magnets has been carried out through Spark Plasma Sintering, resulting in highly aligned nanocrystals, resulting in a high energy product. The next step for improving magnetic performance is mixing hard and soft magnetic phases to prepare exchange-spring magnets. Initial efforts in this regards will be demonstrated. 1. I. Matsui, Jpn J Appl Phys 1, 2006, 45, 8302-8307. 2. S. Tammaruckwattana and K. Ohyama, Ieee Ind Elec, 2013, 7157-7162. 3. E. F. Kneller and R. Hawig, Ieee T Magn, 1991, 27, 3588-3600