It is commonly understood that among the intermetallic phases used for permanent magnets, practically none can fully realize its potential based on the intrinsic magnetic properties. We discuss different reasons leading to this limitation, known as the Brown paradox, and discuss some possible ways of overcoming it. We look into Dy- and Tb-less grain boundary diffused magnets and the scope for the complete elimination of the heavy rare earth elements. Then we compare the intrinsic magnetic properties of (Nd1-xCex)2(Fe1-yCoy)14B single crystals with the extrinsic characteristics of sintered and hot compacted magnets, so-called rare earth balance magnets, made from the very same alloys. Finally, assessing RE-free materials, our results obtained on Mn- and Co-based RE-free single crystals are compared with the hard magnetic properties of Mn-based permanent magnets.

中文翻译：

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无重稀土、无稀土和无稀土磁铁——愿景与现实

众所周知，在用于永磁体的金属间相中，几乎没有一种能够基于固有的磁性来充分发挥其潜力。我们讨论导致这种限制的不同原因，称为布朗悖论，并讨论克服它的一些可能方法。我们研究了不含 Dy 和 Tb 的晶界扩散磁体以及完全消除重稀土元素的范围。然后，我们将 (Nd1-xCex)2(Fe1-yCoy)14B 单晶的内在磁性能与由完全相同的合金制成的烧结和热压实磁体（即所谓的稀土平衡磁体）的外在特性进行比较。最后，评估无稀土材料，