We report results of an investigation of the temperature dependence of the magnon and phonon frequencies in NiO. A combination of Brillouin - Mandelstam and Raman spectroscopies allowed us to elucidate the evolution of the phonon and magnon spectral signatures from the Brillouin zone center (GHz range) to the second-order peaks from the zone boundary (THz range). The temperature-dependent behavior of the magnon and phonon bands in the NiO spectrum indicates the presence of antiferromagnetic (AF) order fluctuation or a persistent AF state at temperatures above the Neel temperature (T=523 K). Tuning the intensity of the excitation laser provides a method for disentangling the features of magnons from acoustic phonons without the application of a magnetic field. Our results are useful for interpretation of the inelastic-light scattering spectrum of NiO, and add to the knowledge of its magnon properties important for THz spintronic devices.
Nickel oxide, in particular in its doped, semiconducting form, is an important component of several optoelectronic devices. Doping NiO is commonly achieved either by incorporation of lithium, which readily occupies Ni sites substitutionally, producing the Li$_{\text{Ni}}$ acceptor, or by supplying reactive oxygen species during NiO film deposition, which leads to the formation of Ni vacancies (V$_{\mathrm{Ni}}$). However, the energetic position of these acceptors in the NiO band gap has not been experimentally determined until today. In this work, we close this knowledge gap by studying rectif…
We present research results on the electronic transport in heterostructures based on p-type nickel oxide (NiO) with the n-type oxide semiconductors zinc oxide (ZnO) and cadmium oxide (CdO). NiO is a desirable candidate for application in (opto-)electronic devices. However, because of its small electron affinity, heterojunctions with most n-type oxide semiconductors exhibit conduction and valence band offsets at the heterointerface in excess of 1 eV. ZnO/NiO junctions exhibit a so called type-II band alignment, making electron-hole recombination the only process by which a current can verticall…
Nickel oxide is a versatile p-type semiconducting oxide with many applications in opto-electronic devices, but high doping concentrations are often required to achieve necessary electrical conductivity. In contrast to many other transparent oxide semiconductors, even moderate levels of doping of NiO can lead to significant optical absorption in the visible spectral range, limiting the application range of the material. This correlation has been reported extensively in literature, but its origin has been unknown until now. This work combines experimental data on optical properties from a variet…
Titanium is commonly added to nickel superalloys but has a well-documented detrimental effect on oxidation resistance. The present work constitutes the first atomistic-scale quantitative measurements of grain boundary and bulk compositions in the oxide scale of a current generation polycrystalline nickel superalloy performed through atom probe tomography. Titanium was found to be particularly detrimental to oxide scale growth through grain boundary diffusion.
The development of new electrochromic materials and devices, like smart windows, has an enormous impact on the energy efficiency of modern society. One of the crucial materials in this technology is nickel-oxide. Ni-deficient NiO shows anodic electrochromism whose mechanism is still under debate. Using DFT+U calculations, we show that Ni vacancy generation results in the formation of hole polarons localised at the two oxygens next to the vacancy. Upon Li insertion or injection of an extra electron into Ni-deficient NiO, one hole gets filled, and the hole bipolaron is converted into a hole pola…
The physics of mutual interaction of phonon quasiparticles with electronic spin degrees of freedom, leading to unusual transport phenomena of spin and heat, has been a subject of continuing interests for decades. Despite its pivotal role in transport processes, the effect of spin-phonon coupling on the phonon system, especially acoustic phonon properties, has so far been elusive. By means of inelastic neutron scattering and first-principles calculations, anomalous scattering spectral intensity from acoustic phonons was identified in the exemplary collinear antiferromagnetic nickel (II) oxide, …
We experimentally investigate the origin of the two-magnon scattering (TMS) in heavy-metal (HM)/ferromagnet (FM)/oxide heterostructures (FM = Co, Ni81Fe19, or Fe60Co20B20) by varying the materials located above and below the FM layers. We show that strong TMS in HM/FM/oxide systems arises primarily at the HM/FM interface and increases with the strength of interfacial spin-orbit coupling and magnetic roughness at this interface. TMS at the FM/oxide interface is relatively weak, even in systems where spin-orbit coupling at this interface generates strong interfacial magnetic anisotropy. We also …
We describe the ground- and excited-state electronic structure of bulk MnO and NiO, two prototypical correlated electron materials, using coupled cluster theory with single and double excitations (CCSD). As a corollary, this work also reports the first implementation of unrestricted periodic ab initio equation-of motion CCSD. Starting from a Hartree-Fock reference, we find fundamental gaps of 3.46 eV and 4.83 eV for MnO and NiO respectively for the 16 unit supercell, slightly overestimated compared to experiment, although finite-size scaling suggests that the gap is more severely overestimated…
Imaging Antiferromagnetic Domains in Nickel-oxide Thin Films by Magneto-optical Voigt Effect
Fudan University（复旦大学）；University of California, Davis（加州大学戴维斯分校）；Dalian Institute of Chemical Physics, Chinese Academy of Sciences（中国科学院大连化学物理研究所）；Shanghai Synchrotron Radiation Facility, Zhangjiang Laboratory, Chinese Academy of Sciences（中国科学院上海同步辐射光源张江实验室）；Oakland University（奥克兰大学）；Collaborative Innovation Center of Advanced Microstructures（先进微结构协同创新中心）
Virtual Synthesis of Nanoscale Systems with Pre-Designed Properties: Fundamentals and Applications. Chapter 7. Nickel Oxide Quantum Dots and Polymer Nanowires
Chiral-Induced Spin Selectivity Effect in a 1 nm Thin 1,1'-Binaphthyl-2,2'-diyl Hydrogenphosphate Self-Assembled Monolayer on Nickel Oxide
Technical University of Darmstadt（达姆施塔特工业大学）；Technical University of Munich（慕尼黑工业大学）；Weizmann Institute of Science（魏茨曼科学研究所）；Chemnitz University of Technology（开姆尼茨工业大学）；Heidelberg University（海德堡大学）；Merck Electronics KGaA（默克电子股份公司）；University of Freiburg（弗赖堡大学）
Reflecting (on) the Nucleation Curve: Negative Surface Energy Stabilizes Nickel Ferrite Nano-Particles in Nuclear Reactor Coolant
我们使用了化学信息的第一性原理方案，计算了氧化镍（NiO）和镍铁氧体（NiFe 2 O 4）的温度依赖性表面能，这两种化合物是已知的沉积在核压水反应堆（PWR）的燃料棒上。这些计算预测负的表面自由能镍铁氧体时，形成的离子在溶液中的PWR条件下的温度，压力和物种浓度。在这些条件下，大块镍铁氧体的热力学产生了从溶解的离子形成固体的自由能的正变化。这些结果和他们的分析，在经典的成核理论提出了一个新的基本关系-反射成核曲线-这揭示了一个以前未认识的方面的理论的相稳定性。这些计算还表明PWR冷却剂中存在稳定的八面体镍铁氧体簇，其在服务条件之外的冷却剂中不会观察到，并且不会通过过滤和目前用于纯化PWR冷却剂的溶剂化离子的捕获的组合来去除。
The service lives of nickel superalloys are often limited by environmental degradation. The present study compares oxidation, sulfidation and hot corrosion at 750C of three variants of a polycrystalline superalloy: a baseline alloy, a variant containing 1wt% Mn and one containing 0.5wt% Si. Mn reduced the oxidation rate without changing the scale morphology. The MnCr2O4 scale formed proved more protective against sulfidation and hot corrosion, but internal sulfides extended the damage depth. Si modified the oxide morphology to a continuous Cr2O3-Al2O3 dual layer. This provided improved protect…
This work reports on temperature-induced out-diffusion and concentration decay of the prominent intrinsic point defect VNi (nickel vacancy) in the wide-gap p-type semiconductor nickel oxide (NiO). VNi can easily be introduced into NiO thin films by offering high oxygen partial pressures during film growth, rendering nonstoichiometric semiconducting structures. However, exposure to lower oxygen supply after growth, e.g. in a standard atmosphere, usually leads to a gradual decrease of film conductivity, because the vacancy concentration equilibrates. In this study, we observe this process in sit…
The series of nickel-oxide compounds LaNiO$_3$ (formal Ni$(d^7)$), La$_2$NiO$_4$ (formal Ni$(d^8)$) and LaNiO$_2$ (formal Ni$(d^9)$) is investigated by first-principles many-body, using a combination of density functional theory, self-interaction correction and dynamical mean-field theory. The characteristics of these different nickelates, in good agreement with available experimental data, is revealed by employing a compound-independent choice for the local Coulomb interactions. The dichotomy within the low-energy dominant Ni-$e_g$ sector of $\{d_{z^2},d_{x^2-y^2}\}$ kind is rising with growi…
Revisiting Jahn--Teller Transitions in Correlated Oxides with Monte Carlo Modeling
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory（斯坦福同步辐射光源，SLAC国家加速器实验室）；Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford（牛津大学化学系无机化学实验室）；Yusuf Hamied Department of Chemistry, University of Cambridge（剑桥大学优素福·哈米德化学系）；Cavendish Laboratory, University of Cambridge（剑桥大学卡文迪许实验室）
Effect of lattice geometry on magnon Hall effect in ferromagnetic insulators
本文研究了各种铁磁绝缘体磁振子的热霍尔效应。对于烧绿石铁磁绝缘体Lu $_2$ V $_2$ O $_7$、Ho $_2$ V $_2$ O $_7$和In $_2$ Mn $_2$ O $_7$，在居里温度$T_C$以下已经观察到有限的霍尔热导率。从温度和磁场的依赖性，得出结论，磁振子是负责的热霍尔效应。基于Dzyaloshinskiii-Moriya（DM）相互作用引起的动量空间Berry曲率的理论可以很好地解释磁振子的霍尔效应。该分析已扩展到具有钙钛矿结构的过渡金属（TM）氧化物。La $_2$、NiMnO $_6$和YTiO $_3$具有畸变的钙钛矿结构，晶胞中含有四个TM离子，热霍尔信号不存在或小得多。另一方面，在另一种铁磁钙钛矿氧化物BiMnO $_3$中，在$T_C$以下可辨别有限的热霍尔响应，其显示具有较大晶胞的轨道有序。烧绿石和钙钛矿绝缘体系中热霍尔效应的存在与否反映了DM诱导磁振子霍尔效应的几何和拓扑特征。
We analyze resonant magneto-elastic interactions between standing perpendicular spin wave modes (exchange magnons) and longitudinal acoustic phonon modes in free-standing hybrid metal-ferromagnet bilayer and trilayer structures. Whereas the ferromagnetic layer acts as a magnetic cavity, all metal layers control the frequencies and eigenmodes of acoustic vibrations. The here proposed design allows for achieving and tuning the spectral and spatial modes overlap between phonons and magnons that results in their strong resonant interaction. Realistic simulations for gold-nickel multilayers show th…
We present a comprehensive numerical study on the kinetics of phase transition that is characterized by two non-conserved scalar order parameters coupled by a special linear-quadratic interaction. This particular Ginzburg-Landau theory has been proposed to describe the coupled charge- and magnetic transition in nickelates and the collinear stripe phase in cuprates. The inhomogeneous state of such systems at low temperatures consists of magnetic domains separated by quasi-metallic domain-walls where the charge-order is reduced. By performing large-scale cell dynamics simulations, we find a two-…
Nickel-based complex oxides have served as a playground for decades in the quest for a copper-oxide analog of the high-temperature superconductivity. They may provide clues towards understanding the mechanism and an alternative route for high-temperature superconductors. The recent discovery of superconductivity in the infinite-layer nickelate thin films has fulfilled this pursuit. However, material synthesis remains challenging, direct demonstration of perfect diamagnetism is still missing, and understanding of the role of the interface and bulk to the superconducting properties is still lack…
