As examples of a high-performance rare-earth magnet, a Sm—Co-based magnet and a Nd—Fe—B-based magnet and so on are known. In these magnets, Fe and Co contribute to an increase in saturation magnetization. Further, in theses magnets, rare-earth elements such as Nd and Sm are contained to bring about large magnetic anisotropy resulting from behaviors of 4f electrons of the rare-earth elements in a crystal field. This makes it possible to obtain a high coercive force and realize the high-performance magnet.
Such a high-performance magnet is mainly used in electric devices such as motors, speakers, and measuring instruments. There is an increasing demand for a reduction in weight and a reduction in power consumption of various kinds of electric devices, and in order to cope with this, there is a demand for a higher-performance permanent magnet whose maximum magnetic energy product (BHmax) is improved. In recent years, a variable magnetic flux motor has been proposed and contributes to an increase in efficiency of the motor.
The Sm—Co-based magnet has a high Curie temperature and thus can realize an excellent motor property at high temperature, but there is a demand for a higher coercive force, higher magnetization, and improvement in squareness ratio. In order for higher magnetization of the Sm—Co-based magnet, increasing the Fe concentration is considered to be effective, but the squareness ratio tends to decrease due to increasing the Fe concentration in manufacturing methods in prior arts. In order to realize a high-performance magnet for motor, a technique of enabling an excellent squareness ratio while improving the magnetization in a composition with a high Fe concentration is requested.
USPTO Backgrounds
USPTO Backgrounds