Theory of the Variations in Paramagnetic Anisotropy Among Different Salts of the Iron Group
Theory of the Variations in Paramagnetic Anisotropy Among Different Salts of the Iron Group
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DOI：
10.1103/physrev.41.208
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发表时间：
1932-07
期刊：
影响因子：
--
通讯作者：
J. V. Vleck
中科院分区：
文献类型：
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作者：
J. V. Vleck
给出了一个理论解释，为什么镍盐几乎是各向同性的磁性，而那些钴表现出超过25%的各向异性，即使Ni++和Co++离子都在F状态，并在周期表中相邻。其原因是晶体斯塔克效应中的能级在从d8 F3（Ni++）到d 7 F4（Co++）的过程中发生了反转。如果晶体场只有菱形对称性，但与立方对称性的偏差相对较小，Penney和Schlapp的前一篇论文中的方法的扩展表明，Ni++中的近各向同性能级将是基态能级，而Co++中的各向异性能级将是基态能级。应特别注意的是，反转纯粹是由于构型d 7和d8之间的差异而存在，并且不需要Ni和Co化合物中的不同晶场。理论预测水合镍盐比钴盐更符合居里定律，并且具有更接近于”仅自旋”值4 NS（S+ 1）（he 4 π mc）2 3 k的居里常数。这与实验相符。其他离子对被引用在铁组中，其中遇到反转现象，伴随着磁性行为的多样性。锰盐近乎完美的磁各向同性是微不足道的，因为Mn++的基态是S 6;轻微的各向异性可能是由于少量初始的j-j耦合或晶体场对轨道角动量恒定性的扭曲，因此轨道磁矩在S态中不会完全消失。
A theoretical explanation is given of why nickel salts are nearly isotropic magnetically, while those of cobalt exhibit over 25 percent anisotropy even though the Ni++ and Co++ ions are both in F states and are adjacent in the periodic table. The cause is an inversion of the levels in the crystalline Stark effect in passing from the configuration d 8 F 3 (Ni++) to d 7 F 4 (Co++). If the crystalline field has only rhombic symmetry, but with the deviations from cubic symmetry comparatively small, extension of the methods in Penney and Schlapp's preceding paper shows that a nearly isotropic level will be the ground level in Ni++, but an anisotropic one in Co++. It is to be particularly noted that the inversion exists purely in virtue of the difference between the configurations d 7 and d 8, and does not require different crystalline fields in Ni and Co compounds. The theory predicts that hydrated Ni salts conform closer to Curie's law than those of Co, and have a Curie constant more nearly equal to the" spin only" value 4 N S (S+ 1)(he 4 π mc) 2 3 k. This agrees with experiment. Other pairs of ions are cited in the iron group in which the inversion phenomenon is encountered, with attendant diversity in magnetic behavior. The nearly perfect magnetic isotropy of manganous salts is trivial, as the ground state of Mn++ is S 6; the slight anisotropy may be due to a small amount of incipient j− j coupling or to distortion of the constancy of orbital angular momentum by the crystalline field, so that the orbital magnetic moment does not vanish completely in S states.