Peking University made important progress in the field of nanocomposite magnets

Recently, Hou Yanglong's research group of Peking University Institute of Technology and Brown University have successfully prepared an L10-FePt-based exchange-coupling composite magnet with a core-shell structure. The size of the soft magnetic shell (Co, Ni, Fe2C) can be adjusted. , Related papers were published online in the internationally renowned journal "Applied Chemistry".

The adjustment of the coupling effect between the grains is an important idea for designing high-performance magnets. Theoretical studies have shown that the exchange coupling in the nanoscale of soft and hard magnetic grains can enable the material to obtain high saturation magnetization of the soft magnetic phase and hard magnetic phase at the same time. The high coercive force, which results in a very high magnetic energy product, so nanocomposite magnets are expected to become a new generation of high-performance magnetic materials. In recent years, it has been a research hotspot in the field of magnetism. However, it is difficult to achieve precise control of the soft and hard magnetic phases at the nanometer scale by traditional methods, and the size and distribution of the magnetic phases can be effectively controlled by the nanochemical method, which is convenient to study the coupling between the two phases and the influence law on the magnetic properties. In turn, the magnetic properties of the composite magnet are optimized.

Hou Yanglong's research group found that the magnetic properties of L10-FePt-based exchange-coupled composite magnets depend on the composition and thickness of the soft magnetic shell layer. Therefore, by constructing composite magnets with different compositions and sizes, the magnetic properties of the magnets can be effectively controlled to meet The needs of different applications.

In addition, the research group proposed a brand-new synthesis scheme to prepare SmCo5 / Co exchange-coupled composite magnets chemically, using Sm [Co (CN) 6] · 4H2O crystals and Co (acac) 2 as precursors wrapped with graphene oxide The final product is obtained through the thermal reduction process at high temperature. The SmCo5 / Co exchange-coupled composite magnet has a typical core-shell structure, in which the core SmCo5 has a single-domain structure, making the magnet have a high coercive force (20.7 kOe), and the shell Co as a soft magnetic layer provides the magnet High saturation magnetization (82 emu / g). The study found that graphene oxide plays an important role in the magnet preparation process. It can effectively control the size of the magnet and help to obtain SmCo5 with high coercivity in the single domain structure. At the same time, SmCo-based exchange coupled composite magnets with different proportions of soft and hard magnetic phases can be further obtained by this method. Related work was recently published in the Scientific Reports journal of Nature Publishing Group.

Chemical design block diagram of SmCo5 / Co exchange-coupling nanocomposite magnet

The first authors of the above research work are Liu Fei, a Ph.D. student at level 09, and Yang Ce, a Ph.D. student at level 08. The research was supported by projects such as the National Major Research Program (973) and the National Outstanding Youth Fund.