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Magnetism in Ca2CoOsO6 and Ca2NiOsO6: Unraveling the Mystery of Superexchange Interactions between 3d and 5d Ions
Chemistry of Materials ( IF 7.2 ) Pub Date : 2016-06-03 00:00:00 , DOI: 10.1021/acs.chemmater.6b00254
Ryan Morrow 1 , Kartik Samanta 2 , Tanusri Saha Dasgupta 2 , Jie Xiong 1 , John W. Freeland 3 , Daniel Haskel 3 , Patrick M. Woodward 1
Chemistry of Materials ( IF 7.2 ) Pub Date : 2016-06-03 00:00:00 , DOI: 10.1021/acs.chemmater.6b00254
Ryan Morrow 1 , Kartik Samanta 2 , Tanusri Saha Dasgupta 2 , Jie Xiong 1 , John W. Freeland 3 , Daniel Haskel 3 , Patrick M. Woodward 1
Affiliation
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In order to rationalize and predict the behavior of compounds containing 5d transition metal ions, an understanding of the local moments and superexchange interactions from which their magnetic properties are derived is necessary. The magnetic and electrical properties of the ferrimagnetic double perovskites Ca2CoOsO6 and Ca2NiOsO6 studied here provide critical insight toward that goal. First-principles density functional theory (DFT) calculations indicate, and experimental measurements confirm, that the Os(VI) moments are directed antiparallel to the Co/Ni moments. X-ray magnetic circular dichroism (XMCD) measurements reveal that the orbital moment on osmium has a magnitude that is approximately 30% of the spin moment, and the two contributions oppose each other. Both the size and direction of the orbital moment are confirmed by the DFT calculations. The size of the Os(VI) total moment is predicted to be 0.6–0.7 μB by DFT calculations. The ferrimagnetic ground state is stabilized by strong antiferromagnetic coupling between the d2 Os(VI) ion and the d8/d7 Ni(II)/Co(II) ion. Not only does the observation of antiferromagnetic coupling violate the Goodenough–Kanamori rules, but also it is unusual in that it becomes stronger as the Os–O–Co/Ni bond angle decreases. This unusual behavior is shown to arise predominantly from coupling between Os t2g orbitals and Ni/Co eg orbitals, mediated by the intervening oxide ion. We further find that both compounds are spin–orbit assisted Mott insulators.
中文翻译：
Ca 2 CoOsO 6和Ca 2 NiOsO 6中的磁性：揭示3d和5d离子之间超交换相互作用的奥秘
为了合理化和预测含有5d过渡金属离子的化合物的行为，必须了解其磁性能所源自的局部矩和超交换相互作用。亚铁磁性双钙钛矿Ca 2 CoOsO 6和Ca 2 NiOsO 6的磁性和电学性质在这里学习可以为实现该目标提供关键的见识。第一性原理密度泛函理论（DFT）的计算表明，并且实验测量结果证实，Os（VI）矩的方向与Co / Ni矩反平行。X射线磁性圆二色性（XMCD）测量表明，on上的轨道矩的大小约为自旋矩的30％，并且这两个作用彼此相反。轨道力矩的大小和方向都可以通过DFT计算得到确认。该Os（VI）的总力矩的大小被预测为0.6-0.7μ乙通过DFT计算。亚铁基态通过d 2 Os（VI）离子与d 8 / d 7之间的强反铁磁耦合而稳定Ni（II）/ Co（II）离子。反铁磁耦合的观察不仅违反了Goodenough–Kanamori规则，而且还很不寻常，因为随着Os–O–Co / Ni键角的减小，它会变得更强。已表明这种异常行为主要是由中间的氧化离子介导的Os t 2g轨道与Ni / Co e g轨道之间的耦合引起的。我们进一步发现，这两种化合物都是自旋轨道辅助的Mott绝缘子。
更新日期：2016-06-03
中文翻译：
Ca 2 CoOsO 6和Ca 2 NiOsO 6中的磁性：揭示3d和5d离子之间超交换相互作用的奥秘
为了合理化和预测含有5d过渡金属离子的化合物的行为，必须了解其磁性能所源自的局部矩和超交换相互作用。亚铁磁性双钙钛矿Ca 2 CoOsO 6和Ca 2 NiOsO 6的磁性和电学性质在这里学习可以为实现该目标提供关键的见识。第一性原理密度泛函理论（DFT）的计算表明，并且实验测量结果证实，Os（VI）矩的方向与Co / Ni矩反平行。X射线磁性圆二色性（XMCD）测量表明，on上的轨道矩的大小约为自旋矩的30％，并且这两个作用彼此相反。轨道力矩的大小和方向都可以通过DFT计算得到确认。该Os（VI）的总力矩的大小被预测为0.6-0.7μ乙通过DFT计算。亚铁基态通过d 2 Os（VI）离子与d 8 / d 7之间的强反铁磁耦合而稳定Ni（II）/ Co（II）离子。反铁磁耦合的观察不仅违反了Goodenough–Kanamori规则，而且还很不寻常，因为随着Os–O–Co / Ni键角的减小，它会变得更强。已表明这种异常行为主要是由中间的氧化离子介导的Os t 2g轨道与Ni / Co e g轨道之间的耦合引起的。我们进一步发现，这两种化合物都是自旋轨道辅助的Mott绝缘子。
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