揭示 5d^{4}双钙钛矿 Ba_{2}YIrO_{6}的磁性本质。

Unraveling the Nature of Magnetism of the 5d^{4} Double Perovskite Ba_{2}YIrO_{6}.

机构信息

Leibniz Institute for Solid State and Materials Research, IFW Dresden, D-01171 Dresden, Germany.

Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany.

出版信息

Phys Rev Lett. 2018 Jun 8;120(23):237204. doi: 10.1103/PhysRevLett.120.237204.

DOI:10.1103/PhysRevLett.120.237204

PMID:29932685

Abstract

We report electron spin resonance (ESR) spectroscopy results on the double perovskite Ba_{2}YIrO_{6}. On general grounds, this material is expected to be nonmagnetic due to the strong coupling of the spin and orbital momenta of Ir^{5+} (5d^{4}) ions. However, controversial experimental reports on either strong antiferromagnetism with static order at low temperatures or just a weakly paramagnetic behavior have triggered a discussion on the breakdown of the generally accepted scenario of the strongly spin-orbit coupled ground states in the 5d^{4} iridates and the emergence of a novel exotic magnetic state. Our data evidence that the magnetism of the studied material is solely due to a few percent of Ir^{4+} and Ir^{6+} magnetic defects while the regular Ir^{5+} sites remain nonmagnetic. Remarkably, the defect Ir^{6+} species manifest magnetic correlations in the ESR spectra at T≲20 K, suggesting a long-range character of superexchange in the double perovskites as proposed by recent theories.

摘要

我们报告了双钙钛矿 Ba_{2}YIrO_{6} 的电子自旋共振（ESR）光谱结果。一般来说，由于 Ir^{5+}（5d^{4}）离子的自旋和轨道动量的强耦合，预计该材料是无磁性的。然而，关于低温下存在强反铁磁序或仅仅是弱顺磁行为的争议性实验报告，引发了关于在 5d^{4}铱酸盐中强自旋轨道耦合基态的普遍接受情景的破裂以及新的奇异磁态的出现的讨论。我们的数据表明，所研究材料的磁性仅归因于少量的 Ir^{4+}和 Ir^{6+}磁性缺陷，而常规的 Ir^{5+}位保持非磁性。值得注意的是，在 T≲20 K 时，缺陷 Ir^{6+}物种在 ESR 光谱中表现出磁相关性，这表明双钙钛矿中超交换具有远程特征，正如最近的理论所提出的那样。