It is proposed that permanent magnets can be made of composite materials consisting of two suitably dispersed ferromagnetic and mutually exchange-coupled phases, one of which is hard magnetic in order to provide a high coercive field, while the other may be soft magnetic, just providing a high saturation J/sub s/, and should envelop the hard phase regions in order to prevent their corrosion. A general theoretical treatment of such systems shows that one may expect, besides a high energy product (BH)/sub max/, a reversible demagnetization curve (exchange-spring) and, in certain cases, an unusually high isotropic remanence ratio B/sub r//J/sub s/, while the required volume fraction of the hard phase may be very low, on the order of 10%. The technological realization of such materials is shown to be based on the principle that all phases involved must emerge from a common metastable matrix phase in order to be crystallographically coherent and consequently magnetically exchange coupled.
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机译：提出了永磁体可以由复合材料制成，该复合材料由两个适当分散的铁磁相和相互交换耦合的相组成，其中之一是硬磁的以提供高矫顽力，而另一种可以是软磁，仅提供高饱和度J / sub s /，并应包裹硬质相区域以防止其腐蚀。这种系统的一般理论处理表明，除了高能量乘积（BH）/ sub max /以外，还可能期望有可逆的退磁曲线（交换弹簧），并且在某些情况下还可能会出现异常高的各向同性剩磁比B / sub r // J / sub s /，而硬相所需的体积分数可能非常低，约为10％。这种材料的技术实现被证明是基于这样的原理，即所涉及的所有相必须从共同的亚稳态基质相中出现，以便在晶体学上相干并因此进行磁交换耦合。
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