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开发兼具高最大磁能积与高居里温度的稀土永磁体，已成为当前应用磁学领域的核心挑战与战略目标.Sm-Fe-N理论磁能积与钕铁硼（ 59 MGOe）相当，但具有更高的居里温度和更强的磁晶各向异性，且不含重稀土和不受钕价格波动影响，是具有高稳定性与高矫顽力潜力的一种新型稀土永磁材料.本研究中，我们系统研究了超强磁晶各向异性Sm-Fe-N中的氮含量/占位、磁结构/超精细场以及Sm/Fe自旋轨道耦合。通过特殊装样与吸收修正，成功获得Sm2Fe17及氮化物的高质量中子衍射图谱.研究表明，N原子择优占据9e间隙位，形成了全氮化合物Sm2Fe17N3.结合57Fe穆斯堡尔谱，发现氮化显著提升了材料的居里温度和基态Fe磁矩，从而增强了其室温磁性能.稳态强磁场测量表明，Sm2Fe17N3室温各向异性场为22.6 T，2 K时超过50 T，具有超强磁晶各向异性，为实现高矫顽力提供了关键基础.通过磁圆二色性技术，确认Sm磁性以轨道磁矩的贡献为主，其强自旋轨道耦合效应是超强磁晶各向异性的物理根源.相比之下，Fe轨道磁矩发生淬灭，使其总磁矩由自旋磁矩贡献.本研究阐明了间隙氮含量/占位与磁晶各向异性的内在关系，揭示稀土Sm/Fe自旋轨道耦合机制，为设计高性能永磁材料提供了重要理论依据.The development of rare-earth permanent magnets that combine high maximum energy product with high Curie temperature has emerged as a central challenge in the field of applied magnets. Sm-Fe-N magnets exhibit a theoretical maximum energy product comparable to Nd-Fe-B (~59 MGOe), along with a higher Curie temperature and greater magnetocrystalline anisotropy. Furthermore, Sm-Fe-N magnets do not rely on scarce heavy rare-earth elements and are immune to price fluctuations of neodymium. These advantages position them as a highly promising rareearth permanent magnet material, offering significant potential for achieving both high stability and coercivity. In this work, using complementary neutron diffraction, 57Fe Mössbauer spectroscopy, highfield magnetic measurements, and X-ray magnetic circular dichroism (XMCD), we systematically investigate nitrogen content and site occupancy, magnetic structure and hyperfine fields, as well as the Sm/Fe spin-orbit coupling in Sm-Fe-N. The specialized sample preparation and absorption correction methods enable the acquisition of high-quality neutron diffraction patterns for Sm2Fe17 and its nitrides. The result reveals that N atoms preferentially occupy the 9e interstitial sites, forming the fully nitrided Sm2Fe17N3. Combined with 57Fe Mössbauer spectroscopy analysis, it is found that the nitridation reaction significantly enhances both the Curie temperature and the ground-state Fe magnetic moment, thereby improving the room-temperature magnetic properties. Furthermore, high-field magnetic measurements reveal that the anisotropy field of Sm2Fe17N3 reaches 22.6 T at room temperature and exceeds 50 T at 2 K. This confirmsthe ultra-strong magnetocrystalline anisotropy of Sm2Fe17N3, demonstrating its significant potential for achieving high coercivity. XMCD measurements demonstrate that the magnetism of Sm is dominated by its orbital magnetic moment, establishing its strong spin-orbit coupling as the physical origin of the ultra-strong magnetocrystalline anisotropy. In contrast, the orbital magnetic moment of Fe is largely quenched, resulting in a magnetic moment that is primarily spin-derived. This work clarifies the intrinsic relationship between the content and site occupancy of interstitial nitrogen atoms and the magnetocrystalline anisotropy, and reveals the spinorbit coupling mechanism involving rare-earth Sm and Fe. These findings provide an important theoretical basis for the design of high-performance permanent magnet materials.
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Keywords:
- Sm-Fe-N /
- rare-earth permanent magnet /
- magnetocrystalline anisotropy /
- magnetic properties
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