Nazir Safdar
Department of Physics, University of Sargodha, Sargodha, 40100 Pakistan.
Sci Rep. 2021 Jan 13;11(1):1240. doi: 10.1038/s41598-020-80265-6.
Using density functional theory calculations, we found that recently high-pressure synthesized double perovskite oxide [Formula: see text] exhibits ferrimagnetic (FiM) Mott-insulating state having an energy band gap of 0.20 eV which confirms the experimental observations (Feng et al. in Inorg Chem 58:397-404, 2019). Strong antiferromagnetic superexchange interactions between high-energy half-filled [Formula: see text]-[Formula: see text] and low-energy partially filled [Formula: see text] orbitals, results in a FiM spin ordering. Besides, the effect of 3d transition metal (TM = Cr, Mn, and Fe) doping with 50% concentration at Ni sites on its electronic and magnetic properties is explored. It is established that smaller size cation-doping at the B site enhances the structural distortion, which further gives strength to the FiM ordering temperature. Interestingly, our results revealed that all TM-doped structures exhibit an electronic transition from Mott-insulating to a half-metallic state with effective integral spin moments. The admixture of Ir 5d orbitals in the spin-majority channel are mainly responsible for conductivity, while the spin minority channel remains an insulator. Surprisingly, a substantial reduction and enhancement of spin moment are found on non-equivalent Ir and oxygen ions, respectively. This leads the Ir ion in a mixed-valence state of [Formula: see text] and [Formula: see text] in all doped systems having configurations of [Formula: see text] ([Formula: see text]) and [Formula: see text] ([Formula: see text]), respectively. Hence, the present work proposes that doping engineering with suitable impurity elements could be an effective way to tailor the physical properties of the materials for their technological potential utilization in advanced spin devices.
通过密度泛函理论计算，我们发现最近高压合成的双钙钛矿氧化物[化学式：见原文]呈现出具有0.20 eV能带隙的亚铁磁（FiM）莫特绝缘态，这证实了实验观察结果（Feng等人，《无机化学》，2019年，第58卷，第397 - 404页）。高能半填充的[化学式：见原文]-[化学式：见原文]和低能部分填充的[化学式：见原文]轨道之间的强反铁磁超交换相互作用导致了FiM自旋序。此外，还探索了在Ni位点以50%浓度掺杂3d过渡金属（TM = Cr、Mn和Fe）对其电子和磁性的影响。结果表明，在B位点掺杂较小尺寸的阳离子会增强结构畸变，进而提高FiM有序温度。有趣的是，我们的结果表明，所有TM掺杂结构都表现出从莫特绝缘到具有有效整数自旋矩的半金属态的电子转变。自旋多数通道中Ir 5d轨道的混合主要负责导电性，而自旋少数通道仍然是绝缘体。令人惊讶的是，在不等价的Ir和氧离子上分别发现了自旋矩的大幅降低和增强。这导致在所有掺杂体系中，Ir离子处于[化学式：见原文]和[化学式：见原文]的混合价态，其构型分别为[化学式：见原文]（[化学式：见原文]）和[化学式：见原文]（[化学式：见原文]）。因此，本工作提出，用合适的杂质元素进行掺杂工程可能是一种有效的方法，可根据材料在先进自旋器件中的技术潜在应用来调整其物理性质。
