Assadi M Hussein N, Shigeta Yasuteru
Center for Computational Sciences, University of Tsukuba Tennodai 1-1-1 Tsukuba Ibaraki 305-8577 Japan
RSC Adv. 2018 Apr 13;8(25):13842-13849. doi: 10.1039/c8ra00576a. eCollection 2018 Apr 11.
The interplay between the coordination environment and magnetic properties in O3 layered sodium transition metal oxides (NaTMO) is a fascinating and complex problem. Through detailed and comprehensive density functional investigations on O3 NaTMO compounds, we demonstrate that the TM ions in O3 NaMnO, NaFeO and NaCoO adopt a high spin state. Structurally, NaMnO and NaPdO undergo Jahn-Teller distortions while NaNbO undergoes puckering distortion. Furthermore, in addition to Jahn-Teller distortion, NaPdO exhibits charge disproportionation as it contains Pd, Pd and Pd species. These distortions stabilize the inter-plane ferromagnetism. Additionally, the inter-plane ferromagnetic coupling is stabilized by kinetic p-d exchange mechanism in undistorted NaCoO, NaNiO and NaTcO. The intra-plane coupling in this family of compounds on the other hand was found to be generally weak. Only NaMnO, NaNiO and NaTcO are predicted to show bulk ferromagnetism with estimated Curie temperatures below ∼50 K.
O3层状钠过渡金属氧化物（NaTMO）中配位环境与磁性能之间的相互作用是一个引人入胜且复杂的问题。通过对O3 NaTMO化合物进行详细而全面的密度泛函研究，我们证明了O3 NaMnO、NaFeO和NaCoO中的过渡金属离子处于高自旋态。在结构上，NaMnO和NaPdO会发生 Jahn-Teller 畸变，而NaNbO会发生褶皱畸变。此外，除了 Jahn-Teller 畸变外，NaPdO由于含有Pd、Pd和Pd物种而表现出电荷歧化。这些畸变稳定了面间铁磁性。此外，在未畸变的NaCoO、NaNiO和NaTcO中，面间铁磁耦合通过动力学p-d交换机制得以稳定。另一方面，发现该系列化合物中的面内耦合通常较弱。只有NaMnO、NaNiO和NaTcO预计会表现出体铁磁性，估计居里温度低于约50K。
