Perovskite rare-earth titanates are prototypical Mott insulators in which ${\mathrm{Ti}}^{3+}$ ions with $3d^1$ electronic configuration exhibit ferromagnetic or antiferromagnetic spin order, depending on the rare-earth size. This peculiar magnetic behavior has, however, been barely studied with element-specific probes, either in bulk or in thin films. The recent finding of fingerprints of ferromagnetism in two-dimensional electron gases at oxide interfaces involving rare-earth titanates has produced a surge of the interest in these complex materials. Harnessing the interfacial magnetic states in these heterostructures calls for a better understanding of their insufficiently explored magnetic states in bulk and especially in thin film form. In this paper, we combine high-resolution transmission electron microscopy with x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) to determine the structural, electronic, and magnetic structure of $\mathrm{GdTi}{\mathrm{O}}_3$ in bulk and thin film form. In both cases, we find that the sample surface is strongly overoxidized but a few nm below, Ti is mostly 3+ and shows a large XMCD. We provide evidence for the ferrimagnetic nature of $\mathrm{GdTi}{\mathrm{O}}_3$ with antialigned Gd and Ti sublattices and show that, just as in antiferromagnetic $\mathrm{LaTi}{\mathrm{O}}_3$ or ferromagnetic $\mathrm{YTi}{\mathrm{O}}_3$, Ti carries no orbital moment.

Nanotubes generated by rolling up transition metal dichalcogenide Janus monolayers are a new class of low-dimensional materials, which are expected to display unique electronic properties compared to their parent two- and three-dimensional structures. Here, we investigate the band structure of $1H$-MoSTe Janus armchair and zigzag nanotubes, which were recently hypothesized to be stable as single-walled structures with radii of only a few nanometers. We first investigate the most stable nanotube sizes and assess the influence of quantum confinement and curvature on the band structures, showing that these are heavily modified by curvature while confinement effects are negligible. The curvature dependence is then further studied by analyzing the band gap dependence on the nanotube radius, where band gap changes as large as 0.5 eV are observed. By investigating the band edge positions and orbital projected density of states for different tube sizes, we find that this high sensitivity is mainly attributed to the Mo $d$ states in the conduction band.

${\mathrm{BaTiO}}_3$ (BT) is the best-known ferroelectric and $\mathrm{Pb}{\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}{\mathrm{O}}_3$ (PMN) is the best-known relaxor ferroelectric, but their solid solutions were so far studied only very scarcely. Here the high-density perovskite ceramic solid solutions of $\left(1-x\right){\mathrm{BaTiO}}_3\text{−}x\mathrm{Pb}{\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}{\mathrm{O}}_3$ (BT-100$x$%PMN, $x=0.075$, 0.10, 0.15) were studied by the infrared reflectivity, time-domain terahertz transmission and microwave spectroscopies (1 MHz–20 THz) and compared with the undoped BT and PMN ceramics. The spectra show presence of a split soft phonon at all temperatures, similar to that observed in BT and PMN. Microwave dielectric dispersion was observed both below and above temperature of the diffuse permittivity maximum. In the case of BT-7.5%PMN and BT-10%PMN, the main dispersion takes place above 1 GHz, in case of the BT-15%PMN, the dispersion covers more homogeneously the 1 MHz–1 THz range. The dielectric response up to the THz range of the BT-10%PMN and BT-15%PMN was fitted with three excitations: soft mode, central mode (lower-frequency component of the split soft phonon), and microwave relaxation, but the soft mode does not soften appreciably and only the latter two excitations contribute substantially to the dielectric permittivity maximum. Dielectric response of the BT-7.5%PMN is similar except for the presence of a second dielectric relaxation in the MHz range, also observed in BT. The relaxations show no PMN-like freezing and can be tentatively attributed to the dynamics of polar nanoregions in the paraelectric phase and to the domain/nanodomain wall dynamics and/or acoustic wave emission and piezoelectric resonances within the grains in the ferroelectric phase. In this way, the BT-100$x$%PMN ceramics cannot be considered as relaxor ferroelectrics, but rather as ferroelectrics with the diffuse phase transition. The broadband dielectric spectra of undoped BT ceramics revealed a split optical soft mode and two additional dielectric relaxations which are mainly responsible for the dielectric anomaly at the ferroelectric phase transition. It supports the phase transition in BT to be at the crossover from a displacive to an order-disorder type.

We investigate a well defined heterostructure constituted by magnetic Fe layers sandwiched between graphene (Gr) and Ir(111). The challenging task to avoid Fe-C solubility and Fe-Ir intermixing has been achieved with atomic controlled Fe intercalation at moderate temperature below 500 K. Upon intercalation of a single ordered Fe layer in registry with the Ir substrate, an intermixing of the Gr bands and Fe $d$ states breaks the symmetry of the Dirac cone, with a downshift in energy of the apex by about 3 eV, and well-localized Fe intermixed states induced in the energy region just below the Fermi level. First principles electronic structure calculations show a large spin splitting of the Fe states, resulting in a majority spin channel almost fully occupied and strongly hybridized with Gr $\pi$ states. X-ray magnetic circular dichroism on the Gr/Fe/Ir heterostructure reveals an ordered spin configuration with a ferromagnetic response of Fe layer(s), with enhanced spin and orbital configurations with respect to the bcc-Fe bulk values. The magnetization switches from a perpendicular easy magnetization axis when the Fe single layer is lattice matched with the Ir(111) surface to a parallel one when the Fe thin film is almost commensurate with graphene.

We present an extensive density functional theory analysis of the structural, electronic, and magnetic properties of isolated $3d$ transition metal adatoms (from Ti to Co) adsorbed on free-standing and Ni(111)-supported graphene. We discuss how the energetics of different adsorption sites is influenced by the filling of $d$-orbital filling across the $3d$ series and identify a direct correlation between the adatom-graphene distance and the degree of charge transfer. The presence of the Ni substrate is found to have stronger impact on the adatoms at the end of the series, leading to modifications of the preferred adsorption site, charge transfer, and spin properties. The magnetic exchange coupling between the spin of the adatom and the Ni magnetization changes as a function of the adatom both in sign (preferred antiferromagnetic exchange for Ti, V, and Cr, and ferromagnetic alignment for the other elements) and in magnitude (from 90 meV for Mn to $\approx 10$ meV for Fe an Co).

Using ab initio density function theory calculations, we have determined the structure of self-interstitial atom (SIA) defects in the most commonly occurring face-centered cubic (FCC) metals. The most stable SIA defects in Al, Ca, Ni, Cu, Pd, and Ag are the $\langle 100\rangle$ dumbbells whereas octahedral SIA configurations have the lowest energy in Pt, Rh, and Th. The relative stability of defect configurations in Sr, Ir, Au, and Pb is less well defined, and calculations suggest that an SIA defect has the $\langle 100\rangle$ dumbbell structure in Sr and Ir, a $\langle 110\rangle$ crowdion/dumbbell structure in Au, and that it adopts an octahedral configuration in Pb. The occurrence of octahedral and $\langle 110\rangle$ crowdion/dumbbell SIA configurations implies that defects diffuse one-dimensionally. This is fundamentally different from the three-dimensional translation-rotation migration characterizing the mobility of a $\langle 100\rangle$ dumbbell. Elastic fields of point defects are defined by their elastic dipole tensors, which we compute for all the defect configurations. The magnetism of a $\langle 100\rangle$ dumbbell in ferromagnetic nickel appears to have little effect on the structure of the defect. The variation of energy and elastic field of an SIA defect in copper is explored in detail as a function of its structural transformation along the migration pathway.

The challenge of parasitic bulk doping in Bi-based 3D topological insulator materials is still omnipresent, especially when preparing samples by molecular beam epitaxy. Here, we present a heterostructure approach for epitaxial ${\left({\mathrm{Bi}}_{1-x}{\mathrm{Sb}}_x\right)}_2{\left({\mathrm{Te}}_{1-y}{\mathrm{Se}}_y\right)}_3$ (BSTS) growth. A thin $n$-type ${\mathrm{Bi}}_2{\mathrm{Se}}_3$ (BS) layer is used as an epitaxial and electrostatic seed which drastically improves the crystalline and electronic quality and reproducibility of the sample properties. In heterostructures of BS with $p$-type BSTS we demonstrate intrinsic band bending effects to tune the electronic properties solely by adjusting the thickness of the respective layer. The analysis of weak antilocalization features in the magnetoconductance indicates a separation of top and bottom conduction layers with increasing BSTS thickness. By temperature- and gate-dependent transport measurements, we show that the thin BS seed layer can be completely depleted within the heterostructure and demonstrate electrostatic tuning of the bands via a back gate throughout the whole sample thickness.

The proposal that very small Néel skyrmions can form in ${\mathrm{SrRuO}}_3/{\mathrm{SrIrO}}_3$ epitaxial bilayers and that the electric field effect can be used to manipulate these skyrmions in gated devices strongly stimulated the recent research of ${\mathrm{SrRuO}}_3$ heterostructures. A strong interfacial Dzyaloshinskii-Moriya interaction was considered as the driving force for the formation of skyrmions in ${\mathrm{SrRuO}}_3/{\mathrm{SrIrO}}_3$ bilayers. Here, we investigated nominally symmetric heterostructures in which an ultrathin ferromagnetic ${\mathrm{SrRuO}}_3$ layer is sandwiched between large spin-orbit coupling ${\mathrm{SrIrO}}_3$ layers, for which the conditions are not favorable for the emergence of a net interfacial Dzyaloshinskii-Moriya interaction. Previously the formation of skyrmions in the asymmetric ${\mathrm{SrRuO}}_3/{\mathrm{SrIrO}}_3$ bilayers was inferred from anomalous Hall resistance loops showing humplike features that resembled topological Hall effect contributions. Symmetric ${\mathrm{SrIrO}}_3/{\mathrm{SrRuO}}_3/{\mathrm{SrIrO}}_3$ trilayers do not show hump anomalies in the Hall loops. However, the anomalous Hall resistance loops of symmetric multilayers, in which the trilayer is stacked several times, do exhibit the humplike structures, similar to the asymmetric ${\mathrm{SrRuO}}_3/{\mathrm{SrIrO}}_3$ bilayers. The origin of the Hall effect loop anomalies likely resides in unavoidable differences in the electronic and magnetic properties of the individual ${\mathrm{SrRuO}}_3$ layers rather than in the formation of skyrmions.

Multi-dimensional defects created by thermodynamic and mechanical condition strongly limit electron mobility by the scattering of charged carriers in semiconducting ${\mathrm{BaSnO}}_3$ (BSO) epitaxial films. Here, we demonstrate that the density of both extended and point defects in heteroepitaxial BSO films can be decreased simultaneously by exploiting surface phase instability and a subsequent redistribution of cations at thermal treatment under different oxygen chemical potentials. By delicately controlling both cation ratio and ambient oxygen partial pressure $p$(${\mathrm{O}}_2$), distinct surface topography and cation redistribution (i.e., BaO segregation or SnO evaporation) were observed along with effective healing of extended defects. Simultaneous control of extended and point defects in La-doped ${\mathrm{BaSnO}}_3$ (LBSO) films during treatment under reducing atmosphere decreased their scattering of charged carriers and yielded an increase in room-temperature electron mobility ${\mu }_{\mathrm{e}}$ by $\sim 104\%(55–112\mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1})$ in initially Sn-excess LBSO films as a result of a complex interplay with the removal of Sn-related species at the surface. Our finding suggests a versatile strategy to further enhance electron transport of perovskite-type stannate films by exploiting chemical heterogeneity on the surface interfacing with the $p$(${\mathrm{O}}_2$)-controlled ambient.

The transparent semiconductor ${\mathrm{In}}_2{\mathrm{O}}_3$ is a technologically important material. It combines optical transparency in the visible frequency range and sizable electric conductivity. We present a study of thermal conductivity of ${\mathrm{In}}_2{\mathrm{O}}_3$ crystals and find that around 20 K, it peaks to a value as high as 5000 $\mathrm{W}{\mathrm{K}}^{-1}{\mathrm{m}}^{-1}$, comparable to the peak thermal conductivity in silicon and exceeded only by a handful of insulators. The amplitude of the peak drastically decreases in the presence of a type of disorder, which does not simply correlate with the density of mobile electrons. Annealing enhances the ceiling of the phonon mean free path. Samples with the highest thermal conductivity are those annealed in the presence of hydrogen. Above 100 K, thermal conductivity becomes sample independent. In this intrinsic regime, dominated by phonon-phonon scattering, the magnitude of thermal diffusivity, $D$, becomes comparable to many other oxides, and its temperature dependence evolves towards $T^{-1}$. The ratio of $D$ to the square of sound velocity yields a scattering time which obeys the expected scaling with the Planckian time.

The structure-thermodynamic stability relationship in vitreous silica is investigated using machine learning and a library of 24 157 inherent structures generated from melt-quenching and replica exchange molecular dynamics simulations. We find that the thermodynamic stability, i.e., enthalpy of the inherent structure $\left(e_{\mathrm{IS}}\right)$, can be accurately predicted by both linear and nonlinear machine learning models from numeric structural descriptors commonly used to characterize disordered structures. We find that short-range features become less indicative of thermodynamic stability below the fragile-to-strong transition. On the other hand, medium-range features, especially those between 2.8 and $\sim 6$ Å, show consistent correlations with $e_{\mathrm{IS}}$ across the liquid and glass regions, and are found to be the most critical to the stability prediction in this study among features from different length scales. Based on the machine learning models, a set of five structural features that are the most predictive of the silica glass stability is identified.

Quaternary $\mathrm{CaO}\text{−}\mathrm{MgO}\text{−}{\mathrm{Al}}_2{\mathrm{O}}_3\text{−}{\mathrm{SiO}}_2$ (CMAS) glasses are important constituents of the Earth's lower crust and mantle, and they also have important industrial applications such as in metallurgical processes, concrete production, and emerging low-${\mathrm{CO}}_2$ cement technologies. In particular, these applications rely heavily on the composition-structure-reactivity relationships for CMAS glasses, which are not yet well established. In this study, we combined force-field molecular dynamics (MD) simulations and density functional theory (DFT) calculations to generate detailed structural representations for a CMAS glass. The generated structures are not only thermodynamically favorable (according to DFT calculations) but also agree with experiments (including our x-ray and neutron total scattering data as well as literature data). Detailed analysis of the final structure (including partial pair distribution functions, coordination number, and oxygen environment) enabled existing discrepancies in the literature to be reconciled and has revealed important structural information on the CMAS glass, specifically (i) the unambiguous assignment of medium-range atomic ordering, (ii) the preferential role of Ca atoms as charge compensators and Mg atoms as network modifiers, (iii) the proximity of Mg atoms to free oxygen sites, and (iv) clustering of Mg atoms. Electronic property calculations suggest higher reactivity for Ca atoms as compared with Mg atoms, and that the reactivity of oxygen atoms varies considerably depending on their local bonding environment. Overall, this information may enhance our mechanistic understanding on CMAS glass dissolution behavior in the future, including dissolution-related mechanisms occurring during the formation of low-${\mathrm{CO}}_2$ cements.

The relationship between material properties and independent variables such as temperature, external field, or time is usually represented by a curve or surface in a multidimensional space. Determining such a curve or surface requires a series of experiments or calculations which are often time and cost consuming. A general strategy uses an appropriate utility function to sample the space to recommend the next optimal experiment or calculation within an active learning loop. However, knowing what optimal sampling strategy to use to minimize the number of experiments is an outstanding problem. We compare a number of strategies based on directed exploration on several materials problems of varying complexity using a Kriging-based model. These include one-dimensional curves such as the fatigue life curve for 304L stainless steel and the Liquidus line of the Fe-C phase diagram, surfaces such as the Hartmann 3 function in three-dimensional space and the fitted intermolecular potential for Ar-SH, and a four-dimensional data set of experimental measurements for ${\mathrm{BaTiO}}_3$-based ceramics. We also consider the effects of experimental noise on the Hartmann 3 function. We find that directed exploration guided by maximum variance provides better performance overall, converging faster across several data sets. However, for certain problems, the tradeoff methods incorporating exploitation can perform at least as well, if not better than maximum variance. Thus, we discuss how the choice of the utility function depends on the distribution of the data, the model performance and uncertainties, additive noise, as well as the budget.

Spins in the “semiconductor vacuum” of silicon-28 (${}^{28}\mathrm{Si}$) are suitable qubit candidates due to their long coherence times. An isotopically purified substrate or epilayer of ${}^{28}\mathrm{Si}$ is required to limit the decoherence pathway caused by magnetic perturbations from surrounding ${}^{29}\mathrm{Si}$ nuclear spins ($I=1/2$), present in natural Si (${}^{\text{nat}}\mathrm{Si}$) at an abundance of 4.67%. We isotopically enrich surface layers of ${}^{\text{nat}}\mathrm{Si}$ by sputtering using high fluence ${}^{28}{\text{Si}}^{-}$ implantation. Phosphorus (P) donors implanted into one such ${}^{28}\mathrm{Si}$ layer with $\sim 3000$ ppm ${}^{29}\mathrm{Si}$, produced by implanting 30 keV ${}^{28}{\text{Si}}^{-}$ ions at a fluence of $4\times {10}^{18}{\mathrm{cm}}^{-2}$, were measured with pulsed electron spin resonance, confirming successful donor activation upon annealing. The monoexponential decay of the Hahn echo signal indicates a depletion of ${}^{29}\mathrm{Si}$. A coherence time of $T_2=285\pm 14\mu \mathrm{s}$ is extracted, which is longer than that obtained in ${}^{\text{nat}}\text{Si}$ for similar doping concentrations and can be increased by reducing the P concentration in the future. Guided by simulations, the isotopic enrichment was improved by employing one-for-one ion sputtering using 45 keV ${}^{28}{\text{Si}}^{-}$ implanted with a fluence of $2.63\times {10}^{18}{\mathrm{cm}}^{-2}$ into ${}^{\text{nat}}\text{Si}$. This resulted in an isotopically enriched surface layer $\sim 100$ nm thick, suitable for providing a sufficient volume of ${}^{28}\mathrm{Si}$ for donor qubits implanted into the near-surface region. We observe a depletion of ${}^{29}\mathrm{Si}$ to 250 ppm as measured by secondary ion mass spectrometry. The impurity content and the crystallization kinetics via solid phase epitaxy are discussed. The ${}^{28}\mathrm{Si}$ layer is confirmed to be a single crystal using transmission electron microscopy. This method of Si isotopic enrichment shows promise for incorporation into the fabrication process flow of Si spin-qubit devices.

Path-integral ab initio molecular dynamics (PI-AIMD) calculations have been employed to probe the nature of chloride ion solvation in aqueous solution. Nuclear quantum effects (NQEs) are shown to weaken hydrogen bonding between the chloride anion and the solvation shell of water molecules. As a consequence, the disruptive effect of the anion on the solvent water structure is significantly reduced compared to what is found in the absence of NQEs. The chloride hydration structure obtained from PI-AIMD agrees well with information extracted from neutron scattering data. In particular, the observed satellite peak in the hydrogen-chloride-hydrogen triple angular distribution serves as a clear signature of NQEs. The present results suggest that NQEs are likely to play a crucial role in determining the structure of saline solutions.

We used $p$-polarized multiple-angle incidence resolution spectrometry (pMAIRS) to investigate a collective orientation barrier (COB) in the growth of organic semiconductor (OSC) films. We demonstrate a temperature-dependent variation in the growth of pentacene (PEN) on $\mathrm{Si}{\mathrm{O}}_2$ films as a model system. The molecular orientation varied from lying to standing as the growth temperature increased. This change suggests that the formation of a standing orientation is thermally activated compared with the lying state. The nucleation of standing-oriented islands occurs by molecular self-assembly at sufficiently high temperatures. Conversely, molecules deposit in a flat-lying state at low temperatures owing to hindrance of the kinetic barrier to reorientation from lying to standing states. The COB is defined as a collective energy barrier for the reorientation processes throughout the growth. The COB is quantitatively estimated from an Arrhenius plot of the probability to form a standing orientation, derived from the dichroic ratio measured by pMAIRS. We found that the COB in the growth of PEN on the $\mathrm{Si}{\mathrm{O}}_2$ system was approximately 0.02 eV, which is a key parameter for determining the molecular orientation. A quantitative evaluation of the COB will be applicable to other systems and enable effective control over the molecular orientation of OSC films.

Motivated by the fact that holes in the ${\mathrm{Ga}}_{1–x}{\mathrm{Mn}}_x\mathrm{As}$ family of ferromagnetic semiconductors play a key role in determining their ferromagnetic properties, we have measured hole concentrations in a series of three ${\mathrm{Ga}}_{1–x}{\mathrm{Mn}}_x{\mathrm{As}}_{1–y}{\mathrm{P}}_y$ alloys grown by molecular beam epitaxy with varying amounts of phosphorus. This was carried out by Hall effect measurements, after eliminating the effect of the anomalous Hall term, and thus isolating the ordinary Hall term that directly provides the concentration of freely moving holes. Comparing these Hall effect results with total hole concentrations obtained from the number of acceptors and compensating donors as given by structural and magnetization measurements, we find that the number of itinerant holes (i.e., holes that contribute to the Hall effect) is significantly less than the total hole concentration. This indicates that a considerable fraction of the holes arising from Mn acceptors are localized. We find, furthermore, that the degree of such localization increases with the concentration of phosphorus in the ${\mathrm{Ga}}_{1–x}{\mathrm{Mn}}_x{\mathrm{As}}_{1–y}{\mathrm{P}}_y$ alloy. Our results indicate that the Curie temperature (and, by extension, other magnetic properties) described by the Zener model in ferromagnetic semiconductors of the ${\mathrm{Ga}}_{1–x}{\mathrm{Mn}}_x\mathrm{As}$ family are determined by the itinerant holes rather than by the total hole concentration. Finally, our results also indicate that ferromagnetism in these alloys vanishes when the total hole concentration falls below a certain Mott-like threshold, suggesting that the holes (both localized and itinerant) reside in the acceptor impurity band created by the presence of Mn acceptors.

The two-dimensional kagome spin lattice structure of Mn atoms in the family of ${\mathrm{Mn}}_{3}X$ noncollinear antiferromagnets are providing substantial excitement in the exploration of Berry-curvature physics and the associated nontrivial magnetotransport responses. Much of these studies are performed in the hexagonal systems, mainly ${\mathrm{Mn}}_3\mathrm{Sn}$ and ${\mathrm{Mn}}_3\mathrm{Ge}$ with the kagome planes having their normal along the [001] direction. In this paper, we report our study in the cubic ${\mathrm{Mn}}_3\mathrm{Pt}$ thin films with their kagome planes normal to the [111] crystal axis. Our studies reveal a hole conduction dominant Hall response with a non-monotonic temperature dependence of anomalous Hall conductivity (AHC), increasing from $9{\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$ at room temperature to $29{\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$ at 100 K, followed by a drop and unexpected sign reversal at lower temperatures. Similar sign reversal is also observed in magnetoresistance measurements. We attribute this sign reversal to the transition from a Berry-curvature-dominated AHC at high temperature to a weak canted ferromagnetic AHC response at lower temperatures below 70 K caused by the reorientation of Mn moments out of the kagome plane. Our above results in thin films of ${\mathrm{Mn}}_3\mathrm{Pt}$ make advances in their integration with room-temperature antiferromagnetic spintronics.

Chemically exfoliated nanoscale few-layer thin ${\mathrm{Li}}_x{\mathrm{CoO}}_2$ samples are studied as a function of annealing at various temperatures, using transmission electron microscopy and electron energy-loss spectroscopy (EELS) in various energy ranges, probing the O-$K$ and Co-$L_{2,3}$ spectra as well as low-energy interband transitions. These spectra are compared with first-principles density functional theory (DFT) calculations. A gradual disordering of the Li and Co cations in the lattice is observed starting from a slight distortion of the pure ${\mathrm{LiCoO}}_{2}R\overline{3}m$ to $C2/m$ due to the lower Li content, followed by a $P2/m$ phase forming at $\approx 200{}^{\circ }\mathrm{C}$ indicative of Li-vacancy ordering, formation of a spinel-type $Fd\overline{3}m$ phase around $250{}^{\circ }\mathrm{C}$, and ultimately a rocksalt-type $Fm\overline{3}m$ phase above $350{}^{\circ }\mathrm{C}$. This disordering leads to a lowering of the band gap as established by low-energy EELS. The Co-$L_{2,3}$ spectra indicate a change of average Co valence from an initial value of about 3.5 consistent with Li-deficiency related ${\mathrm{Co}}^{4+}$, down to 2.8 and 2.4 in the $Fd\overline{3}m$ and $Fm\overline{3}m$, indicative of the increasing presence of ${\mathrm{Co}}^{2+}$ in the higher-temperature phases. The O-$K$ spectra of the rocksalt phase are only reproduced by a calculation for pure CoO and not for a model with random distribution of Li and Co. This indicates that there may be a loss of Li from the rocksalt regions of the sample at these higher temperatures. The conductivity measurements indicate a gradual drop in conductivity above $200{}^{\circ }\mathrm{C}$. This loss in conductivity is clearly related to the more Li-Co interdiffused phases, in which a low-spin electronic structure is no longer valid and stronger correlation effects are expected. Calculations for these phases are based on $\text{DFT}+U$ with Hubbard-$U$ terms with a random distribution of magnetic moment orientations, which lead to a gap even in the paramagnetic phase of CoO.