Permanent Magnet Materials
Permanent Magnets
A new energy paradigm, consisting of greater reliance on renewable energy sources and increased concern for energy efficiency in the total energy lifecycle, has accelerated research in energy-related technologies. Due to their ubiquity, magnetic materials play an essential role in improving the efficiency and performance of devices in electric power generation, conditioning, conversion and transportation. The synthesis, characterisation, and property evaluation of the materials, with an emphasis on structure-property relationships, are key issues in permanent magnets research. Phenomena related to the fundamentals, processing and applications of high performance permanent magnet materials are being explored. Considering future bottle-necks in raw materials, options for recycling of rare-earth intermetallics for hard magnets are developed. Other aspects such as lifetime, corrosion resistance and recycling of magnetic materials are also being studied. Further, the ability to fabricate magnetic thick films (5-300μm) with tailored magnetic properties is the key to design and development of new and powerful magnetic Micro Electro-Mechanical Systems (MEMS).
Figure 1: Hysteresis loops for a permanent M-H (red) and B-H (blue) loop with remanence Mr/Br and coercivity MHc/BHc as characteristic values. The energy product (BH)max is the shaded area in the second quadrant of the B-H loop.
Figure 2: Flow chart illustrating the principal processing routes of high energy density magnets based on micro- and nanocrystalline powders. The right branch shows the three principal ways of maximizing the energy product (BH)max of nanocrystalline magnets (R-T-phase = rare earth-transition metal phase).
O. Gutfleisch et al., J.Magn.Magn.Mater. 242–245 (2002) 1277–1283