Superstructure Ordering Research Articles

Assembly Control at a Low Péclet Number in Ultracentrifugation for Uniformly Sized Nanoparticles

The intrinsic high diffusion rate of colloids at low Péclet number results in an extremely fast crystallization process and instant formation of colloidal crystals, even at an ultracentrifugal field of extremely high intensity. By introducing a small number of clusters in sedimention, it should be possible to slow down the crystallization process, thus making the assembly order tunable in preparative ultracentrifugation experiments. Here, we used sodium dodecyl sulfate-stabilized polystyrene nanoparticles (with a size dispersity of 1.07) dispersed in a solution of high ionic strength. Sedimentation and assembly of these nanoparticles were done using preparative ultracentrifugation at various angular velocities. The sedimentation process was also analyzed in situ by analytical ultracentrifugation in real time. By creating as low as 3% of clusters into these nearly uniformly sized polystyrene nanoparticle dispersions during the sedimentation process, the superstructure order becomes easily tunable between glassy and crystalline. Theoretical calculations complemented the experiments to explain the mechanism of cluster formation in sedimentation. This work provides a novel methodology to produce superstructures with a tunable packing order for colloids at low Péclet number.

Interrelation among superstructural ordering, oxygen nonstoichiometry, and lattice strain of double perovskite Sr2FeMoO6–δ materials

Interrelation among superstructural ordering, oxygen nonstoichiometry, and lattice strain of double perovskite Sr2FeMoO6–δ materials

Interrelation among superstructural ordering, oxygen nonstoichiometry and lattice strain of double perovskite Sr2FeMoO6−δ materials

Double perovskite ceramics Sr2FeMoO6−δ having different amount of antisite disordering and oxygen content are prepared by the solid-phase reaction method using SrFeO2.52(3) and SrMoO4 initial reagents. X-ray and neutron diffraction techniques are used to estimate a modification in the structural parameters as a function of oxygen content and B-site cationic ordering. The reduction in the oxygen content leads to an increase in the unit cell volume, which is mainly associated with an elongation of c-parameter of the tetragonal unit cell and relative expansion of the chemical bonds between Mo/Fe ions and apical oxygen ions. Superstructural ordering observed for the compounds causes a decrease in the unit cell volume, which is accompanied by a reduction in the length of the Mo/Fe–O bonds, located in the basal plane of oxygen octahedra. This modification of the unit cell parameters notably affects a character of the exchange interactions formed between B-site ions thus allowing to control magnetic and transport properties of Sr2FeMoO6−δ ceramics. It is found that comprehensive approach allows a consistent understanding of much debated structural/magnetic behaviors of double perovskite Sr2FeMoO6−δ systems, opening a venue for designing reliable devices based on the half-metallic double perovskite materials.

Сomparative analysis of the change of oxygen nonstoichiometry and superstructural ordering of Fe/Mo cations in the strontium ferromolybdate

Sr2FeMoO6–δ single-phase samples without Fe/Mo cations superstructural ordering (P) and with Curie temperature 407 K were obtained by the solid-phase technique. According to the XRD data, the growth dynamics of the parameter P is nonlinear. In this case, the process of reaching maximum values of P (Pmax) is long and its rate is several times lower than the change of the oxygen index 6–δ. It was found that with increasing temperature of isothermal annealing, P increases and reaches maximal values 88 % at T = 1320 K for 120 h, Pmax = 92 % at T = 1420 K for 100 h, while Pmax = 90 % at T = 1470 K for 45 h. One can assume that the lower values of Pmax at T = 1470 K than at T = 1420 K are due to the influence of thermal energy on the destruction of chain ordering of Fe and Mo cations placed in staggered order. Based on the analysis of P time dependences, two relaxation processes can be found and the dP/dt = ¦(t) can be divided into two regions – I and II. In the region I the relaxation time is shorter than that in the region II. The point is that the ordering of cations in the –O–Fe–O–Mo–O chains in the region I requires atomic displacements by approximately one interatomic distance, whereas in the region II cation displacements occur over long distances with the formation of long[1]chain long-range ordering.

High Pressure Effect on Structural and Electrochemical Properties of Anionic Redox-Based Lithium Transition Metal Oxides

Summary The richness of anionic redox chemistry in the solid state offers new opportunities and a possible paradigm shift in energy storage. The excess capacity that goes beyond conventional theoretical values is attributed to the anionic redox in Li-rich transition metal oxide cathodes for Li-ion batteries. Their electrochemical behavior is thermodynamically determined by structural evolution. To better understand the electrochemical dependence on structural factors, we have induced structural modifications in pristine and electrochemically activated Li1.144Ni0.136Co0.136Mn0.544O2 through high-pressure treatment. A unique cyclical change of structural reordering is observed in the anionic redox-activated material during operando pressure sweep, characterized by a periodic evolution of superlattice peak intensity in synchrotron X-ray diffraction patterns. During the structural reordering period, the bulk compressibility of the material decreases, even becoming negative. These insights elucidate the structural flexibility and metastability of anionic redox-based materials, which can undergo large compressions and structural modifications while delivering good electrochemical properties.

Sodium valproate (VPA) interactions with DNA and histones

Valproic acid/sodium valproate (VPA) constitutes a widely prescribed drug for the treatment of seizure disorders and is a well-known epigenetic agent, inducing the acetylation of histones and affecting the methylation status of DNA and histones, with consequences on gene expression. Because this drug has been recently reported to exert affinity for histone H1, and to a minor degree for DNA, in this work, we investigated a possible interaction of sodium valproate with DNA and histones H1 and H3 using high-performance polarization microscopy and Fourier-transform infrared (FTIR) microspectroscopy. The preparations under examination consisted of hemispheres resulting from drop-casting samples containing VPA-DNA and VPA-histone mixtures. The results indicated that VPA may interact with DNA and histones, inducing changes in the textural superstructure and molecular order of the DNA possibly through van der Waals forces, and in histone H1 and H3 conformations, probably as a result of electrostatic binding between the drug and protein amino acid residues. These results contribute to a better understanding of the pharmacological potential of VPA. The precise sites and mechanisms involved in these interactions would certainly benefit from investigations provided by complementary methodologies.

SMALL-ANGLE SCATTERING OF NEUTRONS ON Sr<sub>2</sub>FeMoO<sub>6–δ</sub> SAMPLES WITH DIFFERENT-DEGREE SUPERSTRUCTURAL ORDERING OF Fe/Mo CATIONS

Single-phase Sr2FeMoO6-δ samples with different-degreesuperstructiral ordering Fe/Mo cations superstructural ordering (P, 76, 86 and 93 %) were obtained by the solid-phase technique. Based on the results of measuring the magnetic characteristics in the samples, we found that an increase in magnetization (26.41, 32.36 and 42.66 A·m2·kg–1), magnetic moment (1.33, 3.07 and 3.58 μB/f.u.) and Curie temperatures (422, 428 and 437 K) withparameter P (76, 86 and 93 %) can be explained by the presence of antistructural defects, as well as antiferromagnetic inclusions. This determines the redistribution of electron density, which is accompanied by the change in electronic configuration of a part of Fe/Mo cations. Based on the temperature dependences of the magnetic moment of the samples measured in ZFC and FC modes, and on small-angle polarized neutron scattering (SANS), we found that the samples are in a magnetically inhomogeneous state. An important result to mention is that we detected the difference between the slope of the SANS curves of samples with different oxygen content, which demonstrates a different microstructure of inhomogeneities. The main inhomogeneities are magnetic inclusions with the dimensions depending on the superstructural ordering of Fe/Mo cations. According to the Porod law, it was shown that the Sr2FeMoO6-δ samples with wave vector values 0.1 > q > 0.002 Å–1 contain polydisperse grains with a smooth surface. For q > 0.1 Å–1 a deviation from the Porod law is observed, confirming the presence of magnetic inhomogeneities with a diameter < 6 nm in the grains.

Phase transformation during Sr2CrMoO6–δ synthesis

The sequence of phase transformations in the process of crystallization of the Sr 2 CrMoO 6 by the solid-phase technique from a stoichiometric mixture of simple oxides SrCO 3 + 0.5Cr 2 O 3 + MoO, has been investigated. It was determined that the synthesis of the strontium chrome-molybdate proceeds through a series of sequential-parallel stages. By means of the differential thermal analysis and thermogravimetric analysis data, it has been established that five clearly expressed endothermal effects were observed in the temperature range 300—1300 K. It was found that during the studies of the phase transformations sequence in the process of the double perovskite synthesis, SrCrO 3 , SrMoO 4 and Sr 2 CrO 4 are the main concomitant compounds. Herewith, it has been observed that with the annealing temperature increase from 300 to 1270 K, the complex compounds SrCrO 4 , SrCrO 3 (350—550 K) and SrMoO 4 , Sr 2 CrO 4 (600—750 K) are emerging initially and practically simultaneously. It has been revealed with a subsequent temperature increase that in the temperature range 940—1100 K, the SrMoO 4 , Sr 2 CrO 4 and SrCrO3 phase concentration dramatically drops with the emerging and growth of the Sr 2 CrMoO 6-δ double perovskite. With that in the range up to 1120—1190 K, the main XRD reflexes intensity for the SrCrO 3 and SrMoO 4 lowers substantially, and their content in the samples at 1170 К is no more than 7,9 %. During a consideration of the derivative of the SrCrO 3 , SrMoO 4 and Sr 2 CrO 4 phase transformation degree (|(dα/dt)|mах), at which their crystallization rates are maximal, it has been determined that |(dα/dt)| mах for the Sr2CrO4 corresponds to the maximal temperature 1045 K, which indicates the presence of considerable kinetic difficulties at the formation of the Sr 2 CrO 4 phase. Thereafter this phase does not disappear and at its appearance the slowing down of the double perovskite growth takes place. On the base of investigations of the phase transformations dynamics for the obtaining of the single-phase Sr 2 CrMoO 6-δ compound with the superstructural ordering of the Cr/Mo cations and improved magnetic characteristics, the SrCrO 3 and SrMoO 4 precursors were used with combined heating modes.

Degree of phase transformations in the conditions of polythermal synthesis of SrBaFeMoO6–δ

The sequence of phase transformations during the crystallization of SrBaFeMoO6–δ by the solid-phase technique from a stoichiometric mixture of simple oxides SrCO3 + BaCO3 + 0.5Fe2O3 + MoO3 was studied. It has been established that the synthesis of barium – strontium ferromolybdate proceeds through a series of sequential - parallel stages. It was found that to minimize the effect of intermediate reaction products, it is necessary to use combined synthesis modes. As a result of using combined synthesis modes for annealing for 20 h and T = 1443 K in vacuum of 10−5 Torr at the pressure of residual oxygen gas 10−8 Pa, it was possible to obtain a single-phase barium – strontium ferromolybdate compound with superstructural ordering of iron and molybdenum cations.

The influence of cation ordering and oxygen nonstoichiometry on magnetic properties of Sr2FeMoO6–x around Curie temperature

Sr2FeMoO6–x polycrystalline samples with different oxygen content (6−x) and various degrees of superstructural ordering of Fe/Mo cations (P) were obtained by the solid-phase method from the SrFeO2.52 and SrMoO4 precursors. From the investigation on the influence of oxygen non-stoichiometry and the P parameter on the magnetic properties of Sr2FeMoO6–x, it was found that with an increase in P and a decrease in the (6−x) value from 5.99 to 5.94, an increase in the magnetization values is observed in the temperature range 77–600 K. For all the Sr2FeMoO6–x samples there is a tendency that P value rises with increasing x, where, accordingly, the volume fraction of regions in which there are no anti-structural defects increases as well. This is also indicated by Mössbauer spectroscopy data, confirming an increase in the area of the S1 sextet corresponding to Fe ions in highly ordered regions and a decrease in the area of the S2 sextet associated with disordered regions. Using the temperature scanning method, the temperatures of the onset and completion of the transition from the paramagnetic to the ferrimagnetic state and, correspondingly, the blurring width of the transition have been estimated. It turned out that with decreasing P, the blurring of the transition increases, which is associated with an increase in the concentration of anti-structural defects.

Chemically driven superstructural ordering leading to giant unit cells in unconventional clathrates Cs8Zn18Sb28 and Cs8Cd18Sb28.

The unconventional clathrates, Cs8Zn18Sb28 and Cs8Cd18Sb28, were synthesized and reinvestigated. These clathrates exhibit unique and extensive superstructural ordering of the clathrate-I structure that was not initially reported. Cs8Cd18Sb28 orders in the Ia3̄d space group (no. 230) with 8 times larger volume of the unit cell in which most framework atoms segregate into distinct Cd and Sb sites. The structure of Cs8Zn18Sb28 is much more complicated, with an 18-fold increase of unit cell volume accompanied by significant reduction of symmetry down to P2 (no. 3) monoclinic space group. This structure was revealed by a combination of synchrotron X-ray diffraction and electron microscopy techniques. A full solid solution, Cs8Zn18−xCdxSb28, was also synthesized and characterized. These compounds follow Vegard's law in regard to their primitive unit cell sizes and melting points. Variable temperature in situ synchrotron powder X-ray diffraction was used to study the formation and melting of Cs8Zn18Sb28. Due to the heavy elements comprising clathrate framework and the complex structural ordering, the synthesized clathrates exhibit ultralow thermal conductivities, all under 0.8 W m−1 K−1 at room temperature. Cs8Zn9Cd9Sb28 and Cs8Zn4.5Cd13.5Sb28 both have total thermal conductivities of 0.49 W m−1 K−1 at room temperature, among the lowest reported for any clathrate. Cs8Zn18Sb28 has typical p-type semiconducting charge transport properties, while the remaining clathrates show unusual n–p transitions or sharp increases of thermopower at low temperatures. Estimations of the bandgaps as activation energy for resistivity dependences show an anomalous widening and then shrinking of the bandgap with increasing Cd-content.

Superstructural Ordering in Hydrogenated Diffusion Membrane Filters of the Pd–In–Ru System

The structural features of diffusion membrane filters are considered by the example of a palladium-based Pd–In–Ru alloy using synchrotron radiation. A comparative analysis of the physical blurring of structural and superstructural reflections is carried out. The influence of membrane hydrogenation on the matrix phase and superstructural domains is shown as well.

Evaluation of crystallographic ordering degree of magnetically active ions in Sr 2FeMoO 6-δ by means of the (101) X-ray peak intensity

Strontium ferromolybdate double perovskite is a promising candidate for room-temperature spintronic applications. Nevertheless, SFMO has not yet found wide application in spintronics. This is attributed to the low reproducibility of its magnetic properties which partially originates from their strong dependence on the ordering degree of Fe and Mo ions in the Bʹ and Bʺ sublattices of double perovskite A2BʹBʺO6. In this work, we have considered an express method of determining the degree of disorder in strontium ferromolybdate. The sublattice occupation with Fe and Mo ions has been estimated for stoichiometric and nonstoichiometric Sr2FeMoO6-δ with a 5% Fe and Mo excess, respectively. We have calculated the intensity ratio between the superstructure (101) XRD peak and the most intense (112 + 200) peak. The calculated curves have been fitted to an analytical expression of a similar case known from literature. The calculation results obtained using the proposed method are within a ± 25 % agreement with Rietveld analysis of experimental data. Thus, this method can be used as an alternative to Rietveld analysis if the exposure time during X-ray diffraction experiment was insufficient. We have discussed the dependence of the I (101)/I (112 + 200) peak intensity ratio on various factors including instrumental broadening of diffraction peaks, peak twinning due to grain size reduction, thin film lattice parameter variation due to substrate lattice mismatch and lattice parameter variation due to oxygen vacancies. The relevance of the method is the evaluation of the degree of superstructure ordering in Sr2FeMoO6-δ without large time consumption for X-ray diffraction pattern recording and Rietveld data processing which may be essential when dealing with large amounts of experimental data.

Double-cell superstructure and vacancy ordering in tensile-strained metallic thin films of Pr0.50Ca0.50CoO3 on LaAlO3

The Pr-based cobaltate $\mathrm{P}{\mathrm{r}}_{0.5}\mathrm{C}{\mathrm{a}}_{0.5}\mathrm{Co}{\mathrm{O}}_{3}$ (PCCO) presents in bulk form a singular simultaneous valence and spin-state transition that turns the metallic state into insulator, and displays a large and ultrafast photoresponse in the insulating phase. Epitaxial thin films of PCCO have been grown by deposition on $\mathrm{LaAl}{\mathrm{O}}_{3}$(001) (LAO) substrate, chosen to minimize the mismatch with the film. The films grow epitaxially with two times the substrate periodicity $(2{a}_{0}\ifmmode\times\else\texttimes\fi{}2{a}_{0}\ifmmode\times\else\texttimes\fi{}2{a}_{0})$ and the long perovskite axis perpendicular to the surface. We report a reduction of the structural symmetry from Pnma (bulk) to $P{2}_{1}{2}_{1}{2}_{1}$ (film). The $P{2}_{1}{2}_{1}{2}_{1}$ symmetry revealed by synchrotron x ray remains at low temperatures. These PCCO films are metallic, and ferromagnetic below ${T}_{\mathrm{C}}=170\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, confirming the stabilization of excited $\mathrm{C}{\mathrm{o}}^{3+}$ spin states and the suppression of the concurrent Co spin-state, valence, and metal-insulator transitions. $Z$-contrast imaging and electron-energy-loss spectroscopy elemental maps reveal long-range ordered oxygen vacancy planes unexpectedly stacking parallel to the interface, in spite of the tensile character of the PCCO/LAO heterostructure. In contrast to the general tendency reported for strained $\mathrm{L}{\mathrm{a}}_{0.5}\mathrm{S}{\mathrm{r}}_{0.5}\mathrm{Co}{\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$ (LSCO) films, we show that a nominal tensile strain can be also compatible with the presence of alternating O vacancy planes parallel to the interface, instead of perpendicular to it. That occurs thanks to the double cell of the film and the formation of the (1/2, 1/2, 1/2) superstructure studied in this work. These results expand the possibilities of controlling interfacial physical properties via engineering of ordered oxygen-defect structures in strongly correlated oxides.

Evolution of the microstructure during the early stages of sintering barium hexaferrite nanoplatelets

Nanoparticles usually exhibit a specific structure and composition, which can influence the development of the microstructure during their sintering. Barium hexaferrite nanoplatelets have a specific, iron-rich structure defined by the termination at the surfaces with the S blocks of their SRS*R* hexaferrite structure (S and R represent a cubic (Fe6O8)2+ and a hexagonal (BaFe6O11)2− structural block, respectively). The unsubstituted and Sc-substituted hexaferrite nanoplatelets were hydrothermally synthesized and fired at different temperatures. A combination of morpho-structural analyses (XRD, SEM, TEM, and aberration-corrected STEM) and magnetic measurements was used to reveal the evolution of the microstructure during sintering. During the initial stages of sintering the nanoplatelets thicken predominantly by the fusion of individual original nanoplatelets. Due to the Fe-rich surfaces of the nanoplatelets, the fusion growth results in an inhomogeneity that leads to the formation of planar defects in the grains and the precipitation of Fe2O3 as the secondary phase. In the Sc-substituted hexaferrite grains, superstructural compositional ordering was detected for the first time. The Sc substitution caused exaggerated grain growth in barium hexaferrite ceramics sintered at 1300 °C.

Sequence of phase transformations at the formation of the strontium chrome-molybdate compound

The sequence of phase transformations in the process of crystallization of the Sr2CrMoO6 by the solid-phase technique from a stoichiometric mixture of simple oxides SrCO3 + 0.5Cr2O3 + MoO, has been investigated. It was determined that the synthesis of the strontium chrome-molybdate proceeds through a series of sequential-parallel stages. By means of the differential thermal analysis and thermogravimetric analysis data, it has been established that five clearly expressed endothermal effects were observed in the temperature range 300−1300 K. It was found that during the studies of the phase transformations sequence in the process of the double perovskite synthesis, SrCrO3, SrMoO4 and Sr2CrO4 are the main concomitant compounds. Herewith, it has been observed that with the annealing temperature increase from 300 to 1270 K, the complex compounds SrCrO4, SrCrO3 (350−550 К) and SrMoO4, Sr2CrO4 (600−750 К) are emerging initially and practically simultaneously. It has been revealed with a subsequent temperature increase that in the temperature range 940−1100 К, the SrMoO4, Sr2CrO4 and SrCrO3 phase concentration dramatically drops with the emerging and growth of the Sr2CrMoO6-δ double perovskite. With that in the range up to 1120–1190 К, the main XRD reflexes intensity for the SrCrO3 and SrMoO4 lowers substantially, and their content in the samples at 1170 К is no more than 7.9%. During a consideration of the derivative of the SrCrO3, SrMoO4 and Sr2CrO4 phase transformation degree (|(dα/dt)|mах), at which their crystallization rates are maximal, it has been determined that |(dα/dt)|mах for the Sr2CrO4 corresponds to the maximal temperature 1045 К, which indicates the presence of considerable kinetic difficulties at the formation of the Sr2CrO4 phase. Thereafter this phase does not disappear and at its appearance the slowing down of the double perovskite growth takes place. On the base of investigations of the phase transformations dynamics for the obtaining of the single-phase Sr2CrMoO6-δ compound with the superstructural ordering of the Cr/Mo cations and improved magnetic characteristics, the SrCrO3 and SrMoO4 precursors were used with combined heating modes.

Study of CoxPt1−x nanoalloy formation mechanism via single-source precursors

This paper is devoted to the study of formation mechanism of metal solid solutions during the thermolysis of single-source precursors in Co–Pt systems with a wide range of superstructural ordering. It is shown that the thermal decomposition of [Pt(NH3)4][Co(C2O4)2(H2O)2]·2H2O salt in helium is critically different from that under hydrogen atmospheres. Thermal degradation under the helium atmosphere is followed by a gradual reduction of platinum and cobalt, and at each thermolysis temperature only one phase is present. At 380 °C an equiatomic Co0.50Pt0.50 solid solution is formed (a = 3.749 (4) Å, Fm−3m space group, V/Z = 13.17 Å3, crystallite size: 5–7 nm). When the precursor is decomposed under a hydrogen atmosphere, the process proceeds mainly through the simultaneous reduction of the platinum and cobalt atoms, and at each temperature section two metal phases are present. The formation of the close to equiatomic Co0.50Pt0.50 solid solution (a = 3.782 (4) Å, Fm−3m space group, V/Z = 13.52 Å3, crystallite size: 7–9 nm) occurs at 450 °C. The calculations of crystallite sizes are confirmed by transmission electron microscopy data.

Small‐Angle Neutron Scattering and Magnetically Heterogeneous State in Sr2FeMoO6–δ

Single‐phase strontium ferromolybdate (Sr2FeMoO6–δ) samples with different degrees of the superstructural ordering of the Fe/Mo cations (P) are obtained from partially reduced SrFeO3–х, SrMoO4 precursors by the solid‐state technology. The study of the temperature dependences of the magnetization measured in the field‐cooling and zero‐field‐cooling modes indicated an inhomogeneous magnetic state of the samples. The presence of magnetic regions of different nature has also been revealed by the small‐angle neutron scattering. For the Sr2FeMoO6–δ samples with different P values and for all values of the magnetic field induction up to 1.5 T and of the scattering vector in the interval 0.1 > q > 0.002 Å−1, the analytical dependence I ∼ q–α obeys the Porod law (α ≈ 4), which corresponds to an object with a smooth and well‐marked surface and polydisperse grain size. Deviations from the Porod law in the q > 0.1 Å−1 region and a weakening of the neutron scattering in applied magnetic fields may be ascribed to magnetic inhomogeneities with diameters D < 6 nm, which are partially destroyed/oriented by magnetic fields В ≥ 1.5 T. It is established that the magnetic homogeneity of the Sr2FeMoO6–δ compound is enhanced with increasing superstructural ordering of the Fe/Mo cations.

Structurally induced modulation of in vitro digestibility of amylopectin corn starch upon esterification with folic acid.

The present study aims to identify how structural modifications of amylopectin corn starch on esterification with folic acid (FA) affects its in vitro digestion. Small angle X-ray scattering (SAXS) confirmed that at low FA esterification (5-10%), the mesophase order showed the absence of any super-structural order. However, a discotic stacking of SF forming columnar hexagonal phases and columnar helical phases (with strong optical anisotropy) was observed upon increasing FA esterification (20-40%). X-ray diffraction (XRD) evidenced the development of a V and B-type molecular packing order in SF with increased FA esterification from 20 to 40%, with a consequential increase in the percentage of slow digestible starch (SDS) and resistant starch (RS). The slower digestion phenomenon displayed a dual-phase behavior, with digestion rates k1 > k2, where k2 being ca. 0.3 of k1. Stacking over packing order appeared to be more influential in limiting the enzymatic action. A k-means clustering analysis of the total digested starch and Fourier transform infrared (FTIR) spectroscopy peak ratios (1000/1022) cm-1 indicated that 0.04 level FA substitution was crucial for slower hydrolysis of SF. This study provides structural insights for developing starch-folic acid ester derivatives that could form building-block copolymers for future development of oral drug/nutraceutical delivery vehicles with tailored starch digestion properties.

The Role of the Fe/Mo Cations Ordering Degree and Oxygen Non‐Stoichiometry on the Formation of the Crystalline and Magnetic Structure of Sr2FeMoO6−δ

Single‐phase Sr2FeMoO6−δ powders with various oxygen indices (δ) and degrees of the superstructural ordering (P) of the Fe/Mo cations are obtained from SrFeO2.52 and SrMoO4 reagents via solid‐state synthesis. It has been established by means of the X‐ray and neutron diffraction that, upon reducing the oxygen content and enhancing the superstructural ordering, the lengths of the Fe–O1 and Mo–O2 bonds in the crystal lattice increase, whereas the Fe–O2 and Mo–O1 bond lengths decrease. At the same time, the volume of the unit cell is reduced, which indicates an enhancement of the covalency degree of the bonds and stimulates a redistribution of the electron density, as well as an increase of the concentration of the spin‐down charge carriers located in the conduction band on the Mo(t2g)↓ orbitals. This circumstance leads to an increase of the density of states at the Fermi level, accompanied by an amplification of the exchange interaction and elevation of the Curie temperature, which points to the leading role of the spin‐polarized charge carriers at the Fermi level in the exchange interaction.