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The structural and magnetic properties of YbMnO3 and Yb0.82Sr0.18MnO3 multiferroics were studied by neutron powder diffraction (NPD), magnetometry and electron spin resonance (ESR) technics in a wide temperature range. Neutron diffraction measurements showed that the substitution of ytterbium ions with strontium ions in hexagonal h - YbMnO3 (space group P63cm) leads to the destabilization of the crystal structure of the last compound and appearance of the mixture of three phases with different structure: hexagonal phase h - Yb0.95Sr0.05MnO3 (space group P63cm), orthorhombic phase o - Yb0.69Sr0.31MnO3 (space group Pbnm), hexagonal phase SrMnO3 (space group P63cm). This fact was proved by the ESR measurements in which a several signals due to the phases of different structure were observed. NPD measurements showed that the magnetic structure of h - Yb0.95Sr0.05MnO3 phase is similar to the magnetic structure of the pure h - YbMnO3 and demonstrate the presence of the antiferromagnetic ordering in the samples. ESR and magnetization measurements of h - YbMnO3 sample proved the presence of the antiferromagnetic correlations and also they showed the appearance of the ferromagnetically correlated nanoregions.

Two porous glassy carbon-based samples doped with Au and Co were investigated. The magnetization study as well as measurements of the nonlinear longitudinal response to a weak ac field (NLR) and electron magnetic resonance give evidences for a presence of magnetic nanoparticles (MNPs) embedded in paramagnetic/ferromagnetic matrix respectively, both samples being in magnetically phase-separated state at temperatures above 300 K. Matrix, forming by paramagnetic centers located in matrix outside the MNPs, reveals exchange interactions providing its ferromagnetic (FM) ordering below TC ≈ 210 K in Au-doped sample and well above 350 K in Co-doped one. For the former, NLR data suggest a percolation character of the matrix long-range FM order, which is mainly caused by a porous amorphous sample structure. Temperature dependence of the magnetization in the Au-doped sample evidences presence of antiferromagnetic (AF) interactions of MNPs with surrounding matrix centers. At magnetic ordering below TC these interactions promote origination of “domains” involving matrix fragment and surrounding MNPs with near opposite orientation of their moments that decreases the magnetostatic energy. On further cooling, the domains exhibit AF ordering below Tcr ∼ 140 K 350 K) and larger remanent magnetization evidences.

The effect of isovalent substitution of rare-earth cations on the phase separation in half-doped manganites was studied on the example of ${\mathrm{Sm}}_{0.32}{\mathrm{Pr}}_{0.18}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3}$ by high-resolution neutron powder diffraction, neutron beam depolarization, second-harmonic magnetic response, and magnetization and resistivity measurements from 4 K up to room temperature and higher. A structural phase transition from the orthorhombic $Pbnm$ phase to a mixture of $Pbnm$ and monoclinic $P{2}_{1}/m$ phases was observed upon cooling. The magnetic ground state was found to be phase-separated into three magnetic phases emerging at different temperatures, viz., ferromagnetic (FM) and antiferromagnetic A and charge-ordered CE types. FM clusters arise far above room temperature in the orthorhombic phase and coalesce upon cooling to produce the long-range FM order below 250 K and to arrive at the percolative FM phase below 120 K. The A- and CE-type orders form in the monoclinic phase at the temperatures 200 K and 120 K, respectively. The Sm/Pr isovalent substitution qualitatively changes the phase separation and significantly increases its temperature range compared to the parent compounds. The results obtained give us knowledge of phase separation occurring in systems with strong electron correlations and extend opportunities for fine-tuning of their properties.

Here are presented investigations of powder and glass-like samples containing carbon nanoparticles, not intentionally doped and doped with Ag, Au and Co. The neutron diffraction study reveals an amorphous structure of the samples doped with Au and Co, as well as the magnetic scattering due to a long-range FM order in the Co-doped sample. The composition and molecular structure of the sample doped with Au is clarified with the NMR investigations. The temperature dependence of the magnetization, M (T), exhibits large irreversibility in low fields of B=1–7 mT. M (B) saturates already above 2 T at high temperatures, but deviates from the saturation behavior below ~50 (150 K). Magnetic hysteresis is observed already at 300 K and exhibits a power-law temperature decay of the coercive field, Bc (T). The macroscopic behavior above is typical of an assembly of partially blocked magnetic nanoparticles. The values of the saturation magnetization, Ms, and the blocking temperature, Tb, are obtained as well. However, the hysteresis loop in the Co-doped sample differs from that in other samples, and the values of Bc and Ms are noticeably increased.

The magnetic, transport and structural properties are studied for La 0.83 Sr 0.17 MnO 3 and La 0.82 Sr 0.18 CoO 3 single crystals with nearly the same doping and the metallic ground state. Their comparisons have shown that ferromagnetic clusters originate in the paramagnetic matrix below Т ⁎ >T C in both samples and exhibit similar properties. This suggests the possible universality of such phenomena in doped mixed-valence oxides of transition metals with the perovskite-type structure. The cluster density increases on cooling and plays an important role on the physical properties of these systems. The differences in cluster evolutions and scenarios of their insulator–metal transitions are related to different magnetic behaviors of the matrixes in these crystals that is mainly due to distinct spin states of the Mn 3+ and Co 3+ ions.

Results of structural neutron diffraction study and data on the transport and magnetic properties (the linear and nonlinear (second and third order) susceptibilities) are presented for the La1-xSrxCoO3 and La1-xCaxCoO3 at x = 0.15 single crystals. It is founf that these compounds are insulators and exhibit the rhombohedral R3-c space group. According to the magnetic measurements, the development of the ferromagnetic (F) clustered state proceeds into three stages. On cooling, during the first stage, the F clusters nucleate at the preferential sites that are likely produced by variation in oxygen and doping stoichiometry. The second stage is characterized by sharp increasing the concetraion of the isolated F clusters on cooling. This is the process of the homogeneous nucleation. A coalescence of the isolated F clusters into some large-scale complexes containig some ammount of the domains is associated with the third stage. Note that it is the typical behavior observed at a first order phase transition. The data allow one to determined reliably the temperature boundaries of the stages.

Results of structural neutron diffraction study and data on the transport and magnetic properties (the linear and nonlinear (second and third order) susceptibilities) are reported for the La1-xSrxCoO3 (x = 0.18 and 0.2) polycrystals. The data on the linear and third-order susceptibilities show indications of a long - range ferromagnetic ordering with the Curie temperature (TC) about 180 K. Measurements of the second harmonic of the magnetization in the parallel ac and steady (H) magnetic fields (M2(H,T)) reveal the appearance of ferromagnetic clusters in a paramagnetic matrix below some temperature (T*) above TC. The characteristics of this clustered state and the stages of its temperature evolution are reliably determined since the non-ferromagnetic matrix affects weakly this state. It is found that a spontaneous nucleation of the ferromagnetic clusters occurs below T*, and their concentration increases sharply on cooling. Upon further decreasing temperature, the isolated clusters coalesce, leading to a percolative - type origination of a ferromagnetism. The M2(H,T) response of isolated clusters and its T-variation, including the onset of the coalescence, are very close to those found in the doped manganites, which supports an assumption on a common origin of the clustered state in these compounds.

We have synthesized the double-layer Aurivillius phase Bi(2)LnNbTiO(9) where Ln = Nd-Gd, Bi. All compounds adopt the orthorhombic polar space group A2(I)am. The magnetic Ln-ion occupies the cuboctahedral position in the middle of the perovskite double-layer, and thus controls the octahedral tilt of the perovskite block. This tilt modifies the ferroelectric displacement of the (Nb,Ti) towards the octahedral faces. This provides a mechanism to systematically modify the polarization. Mn-substitution on the (Nb.Ti) site for Ln = Bi is homogeneous up to x = 0.2. The magnetic moments of In do not order down to 5 K. (C) 2010 Elsevier Ltd. All rights reserved.

The electronic, structural and magnetic phase diagram of the colossal magnetoresistive Sm 1− x Sr x MnO 3 (0.16≤ х ≤0.67) manganites is constructed on the basis of their systematic studies by high-resolution neutron powder diffraction. It is shown the tendency of researched system to formation of the phase-separated states on crystallographic as well as, in the even greater extent, on magnetic level. A clear correlation between fine specific features and temperature evolution of crystal structures, spin ordering of the manganese ions, and the physical properties of the samarium–strontium series of manganites obtained from temperature magnetic and transport measurements is demonstrated. It was found that ground state of Sm–Sr manganites shows very various physical properties depending first of all on the doping level х and, for given х , determined by two distortion parameters, namely, the average A -cation size r A > and the local A -cation size mismatch σ 2 .

We present the results of a study of electron-doped Sm1−xSrxMnO3 (x>0.5) perovskite manganites by combining high-resolution neutron powder diffraction with measurements of resistivity, magnetization and magnetic susceptibility. Although investigated Sm0.45Sr0.55MnO3 and Sm0.37Sr0.63MnO3 compounds belonging to the same phase diagram area differ significantly in the strontium content, they are homogeneous antiferromagnetic (AF) insulators and do not exhibit CMR. They have different crystallographic symmetries (orthorhombic Pbnm and tetragonal I4/mcm, respectively) in the entire temperature range under study (1.5–288 K), differ in the type of spin ordering at low temperatures (AF-A and AF-C), are characterized by different orbital polarizations (dx2−y2 and d3z2−r2), and possess two- and one-dimensional magnetic properties, respectively. The lack of magnetoresistance for these compositions is explained by the lack of coexisting magnetic phases involving double exchange ferromagnetism, in contrast to what is observed for the magnetoresistive Sm1−xSrxMnO3 compounds, that is with x⩽0.52.

The magnetic and structural phase diagram of perovskite manganites Sm1 − xSrxMnO3 (0.16 ≤ x ≤ 0.67) are constructed based on systematic studies by high-resolution neutron powder diffraction. It is shown that there is a clear correlation between fine specific features and temperature evolution of crystal structures and the corresponding types of low-temperature magnetic ordering. Correlations were elucidated between the crystal structure, spin ordering of the manganese ions, and the physical properties of the samariumstrontium series of manganites obtained from temperature magnetic and transport measurements.

The 152Sm0.37Sr0.63MnO3 manganite is investigated using neutron diffraction. The parameters of the crystal and magnetic structures of the manganite are determined. The diffraction data are compared with the transport and magnetic characteristics of this compound. A comparison is performed between the 152Sm0.37Sr0.63MnO3 and 152Sm0.45Sr0.55MnO3 manganites. Although these compounds differ insignificantly in the strontium doping level, are homogeneous antiferromagnets, and do not exhibit a colossal negative magnetoresistance, they have different crystal symmetries (tetragonal I4/mcm and orthorhombic Pnma), differ in the type of spin ordering (C-type antiferromagnetic and A-type antiferromagnetic ordering), are characterized by different orbital polarizations (\( d_{3z^2 - r^2 } \) and \( d_{x^2 - y^2 } \)), and possess one-and two-dimensional magnetic and transport properties, respectively. The critical concentration range in which samarium strontium manganites undergo a concentration structural transition from the orthorhombic to tetragonal crystal symmetry with a change in the type of orbital and magnetic order is revealed.

The influence of the replacement of Mn ions in the La0.7Ca0.3Mn1 − y Fe y O3 compounds (0 ≤ y ≤ 0.09) by another transitional metal, Fe, was studied. The radii of both ions are almost identical, which makes the effect of the transitional metal on the physical properties of manganites more transparent. The crystal structure of three samples (with y = 0, 0.03, 0.09) is studied in the temperature range T = 1.5–300 K by neutron powder diffraction. All investigated samples belong to the orthorhombic space group Pnma (62). It is confirmed that Fe ions occupy the Mn positions in the unit cell. As the Fe concentration increases, the saturation value of the spontaneous magnetic moment and the Curie temperature decrease, but the ground state remains ferromagnetic for 0 ≤ y ≤ 0.1. The saturation values of the magnetic moments at T = 1.5 K are m FM = 3.72(3), 3.40(3), and 3.27(3) μ B /Mn for the samples with an Fe concentration y = 0, 0.03, and 0.09, respectively.

The atomic and cluster structure of hydrogen-treated Cu/ZnO (the major component of methanol synthesis catalysts) was studied using Bragg powder and small-angle neutron diffraction. Isotopic substitution of Cu and H was used to obtain reliable results indicating Cu and H clustering. The clusters form on the boundaries of ZnO particles and have a complex structure: a copper cluster surrounded by an adsorbed hydrogen shell has a hydrogen core. It can be assumed that this cluster configuration has a strong effect on the catalytic activity of these compounds.

The lightly doped Nd 1− x Ca x MnO 3− δ ( x = 0.08 , 0.12; δ ⩽ 0.06 ) manganites have been investigated by means of X-ray, neutron powder diffraction, magnetization and AC magnetic susceptibility measurements. It has been shown that complex magnetic behavior of the samples observed at low temperatures can be adequately described using a magnetic phase separation model. In the framework of this model, the antiferromagnetic and ferromagnetic phases have different sign of the f–d exchange. The neodymium magnetic moments start to be ordered near the Neel temperature (Curie temperature). They are directed parallel to the moments of the manganese ions in the ferromagnetic phase, and opposite to this direction in the antiferromagnetic phase. The first-order magnetic phase transition associated with reorientation of the magnetic moments of the ferromagnetic phase along the Nd magnetic moments in the antiferromagnetic phase is observed for the samples from an intermediate range of hole concentration near T eff ∼ 9 K.

As t udy of crystal structure, elastic, and magnetic properties of low-doped Nd1−x Cax MnO3 (x 0.15) perovskites has been carried out. The ferromagnetic component is shown t oi ncrease under hole doping and, simultaneously, the temperature of the orbital order–disorder phase transition decreases. The mechanism of the concentrational transition from a weak ferromagnetic state (x = 0) to a ferromagnetic one (x > 0.15) is discussed using a two-phase model, according t ow hich the samples consist of weak ferromagnetic and ferromagnetic phase se xchange coupled at their boundary. It is found that interaction between different magnetic phases leads to spin reorientation which takes place for 0.06 x 0. 1c ompounds around Teff ∼ 9K . In the temperatur er ange from 5 to 20 K, metamagnetic behaviour is revealed for the Nd0.92Ca0.08MnO2.98 sample. H versus T as well as T versus x magnetic phase diagrams, which are characterized by the missing of a canted phase, are proposed. The appearance of orientational transitions is explained on the basis of a magnetic analogue of the Jahn–Teller effect taking into account that the magnetic moment so f Nd ions are ordered parallel to the moments of Mn ions in the ferromagnetic phase, and opposite to the direction of the weak ferromagnetic vector at T > Teff in the weak ferromagnetic phase.

The maximum solid solubility of gallium in the perovskite-type La 1− x Sr x Fe 1− y Ga y O 3− δ ( x =0.40–0.80; y =0–0.60) was found to vary in the approximate range y =0.25–0.45, decreasing when x increases. Crystal lattice of the perovskite phases, formed in atmospheric air, was studied by X-ray diffraction (XRD) and neutron diffraction and identified as cubic. Doping with Ga results in increasing unit cell volume, while the thermal expansion and total conductivity of (La,Sr)(Fe,Ga)O 3− δ in air decrease with gallium additions. The average thermal expansion coefficients (TECs) are in the range (11.7–16.0)×10 −6 K −1 at 300–800 K and (19.3–26.7)×10 −6 K −1 at 800–1100 K. At oxygen partial pressures close to atmospheric air, the oxygen permeation fluxes through La 1− x Sr x Fe 1− y Ga y O 3− δ ( x =0.7–0.8; y =0.2–0.4) membranes are determined by the bulk ambipolar conductivity; the limiting effect of the oxygen surface exchange was found negligible. Decreasing strontium and gallium concentrations leads to a greater role of the exchange processes. As for many other perovskite systems, the oxygen ionic conductivity of La 1− x Sr x Fe 1− y Ga y O 3− δ increases with strontium content up to x =0.70 and decreases on further doping, probably due to association of oxygen vacancies. Incorporation of moderate amounts of gallium into the B sublattice results in increasing structural disorder, higher ionic conductivity at temperatures below 1170 K, and lower activation energy for the ionic transport.

The structural study of Sm 0.2 Ca 0.8 MnO 3 and Sm 0.2 Ca 0.8 Mn 0.9 Ru 0.1 O 3 versus temperature has been carried out by neutron diffraction and electron microscopy in connection with the magnetic and transport properties. A structural transition from a Pnma paramagnetic insulating structure to a P2 1 /m C-type antiferromagnetic insulating state at T N ≈150 K is observed for the undoped phase. This low temperature monoclinic structure results from a cooperative Jahn–Teller (JT) distortion of manganese cations, hindering the appearance of magnetoresistance in Sm 0.2 Ca 0.8 MnO 3 . In contrast, the Ru-doped phase, which exhibits two magnetic transitions at T C ≈200 and T N ≈110 K, keeps the Pnma structure in the whole temperature range, from 4 to 300 K, showing that Ru-doping destabilizes the JT effect. The influence of ruthenium doping upon the structure and the appearance of ferromagnetism and metallicity in Sm 0.2 Ca 0.8 MnO 3 is discussed by comparing its behavior with those of the x =0.90, 0.85, and 0.80 samples in the Sm 1− x Ca x MnO 3 series.

The title compound was synthesized by reaction of N-(azidomethyl)thiourea or N-(tosylmethyl)thiourea with α-phenylsulfonylacetophenone in the presence of sodium hydride followed by p-toluenesulfonic acid treatment of the obtained N-[3-oxo-3-phenyl-2-(phenylsulfonyl)propyl]thiourea. The molecular and crystal structure of 6-phenyl-5-phenylsulfonyl-1,2,3,4-tetrahydropyrimidine-2-thione (C14H13N2S2O2; space group P21/a; Z=4; a=17.396(1) Å, b=5.887(1) Å, c=15.665(2) Å, β=104.89(1)o) have been determined and refined from neutron (the neutron diffraction was very effective for describing of this system due to using of partial hydrogen-deuterium substitution) powder diffraction data using grid search and a Rietveld procedures. The crystal structure is formed by centrosymmetric hydrogen-bonded dimers along a axis.

Investigations made by susceptibility measurements and neutron diffraction experiments on the TbTi0.85Mo0.15Ge compound are reported. This compound crystallizes in the tetragonal structure of the CeScSi-type (space group, 14/mmm.). It exhibits two ferromagnetic transitions at TC1= 280(3) K and TC2 = 75(3) K. Below the first magnetic transition, the magnetization value and coercive field are 2.6 μB and 0.1 T, respectively, at 120 K. The magnetic structure consists of Tb ferromagnetic (001) layers (μTb=8.01(9) μB at 120 K). Below the second magnetic transition, the maximum magnetization is not reached and the coercive field is 1 T at 5 K. The magnetic structure consists of Tb ferromagnetic layers ferromagneticaly coupled along the c axis with the sequence (0, Mx, Mz)–(0, Mx, Mz)–(Mx, 0, Mz)–(Mx, 0. Mz) and at 1.5 K, Mx=1.15(8) μB, M=9.34(13) μB, M=9.41(13) μB (Mx is the projection of the magnetic moment on the XY plane, Mz the projection of the magnetic moment on the c axis). In this compound, no local moment was detected on the (Ti0.85Mo0.15) site.

Results are presented of studies of the 154Sm1−x SrxMnO3 system using neutron powder diffraction and small-angle polarized neutron scattering. An analysis of the neutron diffraction spectra showed that at T < 180 K these exhibit typical Jahn-Teller distortions of the manganese-oxygen octahedrons which persist under further cooling and on transition of the sample to a metallic magnetically ordered state. The magnetic contribution to the diffraction is satisfactorily described using the (A x (A y )F z ) model and is interpreted as the coexistence of ferromagnetic and antiferromagnetic phases. The exaggerated widths of the diffraction lines indicate an appreciable contribution from microdeformations evidently associated with the inhomogeneity of the system. Small-angle polarized neutron scattering showed that the Sm system for x = 0.4 and 0.25 is magnetically inhomogeneous in the low-temperature phase. Ferromagnetic correlations occur on scales of around 200 A and having dimensions greater than 1000 A which, combined with the temperature hysteresis of the magnetic small-angle scattering intensity observed for an x = 0.4 sample in the low-temperature phase, suggests that the transition is of a percolation nature.

The investigation of two perovskite manganites with the same carrier concentration of 0.1 electron per Mn has been performed using neutron powder diffraction and electron microscopy, and completed with transport and magnetic measurements. For ${\mathrm{Sm}}_{0.1}{\mathrm{Ca}}_{0.9}{\mathrm{MnO}}_{3},$ whatever the temperature (from 2 to 300 K), a unique crystalline structure (Pnma space group) is observed. The magnetic state below ${T}_{N}{=T}_{C}=110\mathrm{K}$ is phase separated, consisting of ferromagnetic domains of different sizes ranging from small clusters to macroscopic regions, which are embedded in an antiferromagnetic G-type matrix. The high conductivity observed in ${\mathrm{Sm}}_{0.1}{\mathrm{Ca}}_{0.9}{\mathrm{MnO}}_{3}$ at low temperature is established through a percolation of the ferromagnetic domains. At room temperature, the structure of the analogous compound ${\mathrm{Pr}}_{0.1}{\mathrm{Sr}}_{0.9}{\mathrm{MnO}}_{3}$ is cubic $(Pm3m$ space group). At low temperature $(Tl200\mathrm{K}),$ this manganite exhibits a complex microstructure, consisting of an intergrowth of G and C-type antiferromagnetically ordered layers, both from tetragonal $I4/mcm$ structure, with appreciable lattice distortion. In agreement with the insulating behavior of ${\mathrm{Pr}}_{0.1}{\mathrm{Sr}}_{0.9}{\mathrm{MnO}}_{3}$ at low temperature, no ferromagnetism is observed.

The investigation of Sm 0.15 Ca 0.85 MnO 3 and Pr 0.15 Sr 0.85 MnO 3 manganites shows that both oxides exhibit a metal to insulator transition around 110 and 260 K, respectively, but they differ by the existence of CMR properties for the former, in contrast to the latter. The neutron powder diffraction and electron microscopy studies show that the resistive transitions are linked to the structural and magnetic ones. Both oxides are C-type antiferromagnets at low temperature, with a similar d 3 z 2 − r 2 orbital polarization which is associated with ordering of the orbitals into chains, no charge ordering being detected. Although they exhibit a similar distortion of their MnO 6 octahedra, these two C-type antiferromagnets differ mainly by the tilt arrangement of the octahedra, leading to the P2 l /m and I4/mcm structures for Sm 0.15 Ca 0.85 MnO 3 and Pr 0.15 Sr 0.85 MnO 3 respectively. Moreover, few percents of a G-type antiferromagnetic phase has also been evidenced in Sm 0.15 Ca 0.85 MnO 3 . The existence of this secondary phase is discussed in connection with its CMR properties.

The crystal and molecular structures of 2-[1-(2-aminoethyl)-2-imidazolidinylidene]-2-nitroacetonitrile [C7H11N5O2; space group P21/n; Z = 4; a = 7.4889 (8), b = 17.273 (2), c = 7.4073 (8) Å, β = 111.937 (6)°], (I), and 2,6-diamino-5-hydroxy-3-nitro-4H-pyrazolo[1,5-a]pyrimidin-7-one monohydrate [C6H6N6O4·H2O; space group P21/n; Z = 4; a = 17.576 (3), b = 10.900 (2), c = 4.6738 (6) Å, β = 92.867 (8)°], (II), have been determined from X-ray, synchrotron and neutron powder diffraction data using various methods. The structures were originally solved from Guinier photographs with a grid search procedure and the program MRIA using a priori information from NMR and mass spectra on the possible geometry of the molecules. Because the conformation of molecule (I) changed during the bond-restrained Rietveld refinement, solvent water was found in (II) and, moreover, as both Guinier patterns were corrupted by texture, high-resolution texture-free synchrotron data were collected at the BM16 beamline, ESRF, to confirm the original results. Using the set of |F| 2 values derived from the synchrotron patterns after full-pattern decomposition procedures, the structures of (I) and (II) were solved by direct methods via SHELXS96, SIRPOW.92 and POWSIM without any preliminary models of the molecules, and by Patterson search methods via DIRDIF96 and PATSEE with the use of rigid fragments from each of the molecules. The neutron patterns allowed (I) and (II) to be solved using the grid search procedure and correct initial models of the molecules including H atoms. The results obtained from powder patterns measured on different devices demonstrate the high level of reproducibility and reliability of various powder software and equipment, with a certain preference for synchrotron facilities.

Diffraction of high-monochromaticity (δλ/λ⩽10 −6 ) , short-wavelength (λ=0.003 nm ) gamma radiations was used to study the defect structure changes arising during different treatments of silicon single crystals and p−n structures. Absolute values of the integrated reflectivity for a few orders of reflection as well as rocking curves were derived by ω-step scanning in transmission geometry. The theoretical foundations relevant to the interpretation of the experimental data and characterization of the samples are given. The main advantages of γ-ray diffraction, in particular high sensitivity to lattice distortions, have been demonstrated in a study of the defect structure changes taking place during crystal growth, neutron transmutation doping and device structure formation. The investigations showed high efficiency of the heat treatment in chlorine-containing atmosphere as a means of decreasing the structural defect concentration in single crystals and p−n structures. The role of non-equilibrium intrinsic point defects in defect formation during thermochemical treatments is discussed.

The results of structure refinements of NaNO2 embedded in porous glass are presented. It is shown that NaNO2 forms complex dendrite clusters in porous glass. For the first time, the details of the structure, including anisotropic thermal parameters, are determined both below and above the ferroelectric phase-transition (PT) temperature Tc and it is shown that the amplitudes of thermal ion motions increase drastically upon heating. This fact could be attributed to the possible formation of a ‘pre-melted’ state at temperatures more than a hundred degrees below Tmelt (554.1 K) of the bulk material. On cooling the ferroelectric PT suppresses this ‘looseness’ and, below Tc, the structure is identical to that of bulk NaNO2, but the thermal displacements remain strongly anisotropic.

We report results of neutron diffraction measurements on tetragonal (P4/mmm) Sm zero matrix superconductors (152,154) Sm(0)Ba 2 Cu 2.76 Fe 0.24 O 7+ δ with T c in the range 59 to 70 K, and similar YBa 2 Cu 2.76 Fe 0.24 O 7+ δ samples with Fe and Cu isotopes. The investigations were performed in the temperature range 8 to 300 K using three different high resolution diffractometers. Analysis of the measurements shows that Fe is distributed with approximately equal probability between the Cu(1) and Cu(2) positions. The temperature dependences of the lattice parameters of the Sm and Y systems showing similar nonlinear variations and no abrupt changes, which might be characteristic of intermediate valence instabilities in Sm, were observed.

The crystal structure of the title compound, (4-amino­phenyl)phenyl­diazenium chloride, C12H12N3+·Cl−, was determined from X-ray laboratory powder data, and the protonation on the azo group was confirmed by the neutron powder data. The cations form stacks along [100], while the chloride anions form hydrogen bonds to all three H atoms attached to N atoms. The absorption maximum of the crystalline salt is shifted bathochromically by 850 cm−1, compared with that in ethanol solution.

Single crystals of the isotopic `zero-matrix' samarium hexaboride (152Sm154Sm11B6) have been prepared by a modified variant of the high-temperature solution growth method. The crystals were studied by high-resolution powder (HRP) neutron diffraction and X-ray single-crystal diffractometry. The occurrence of vacancies at the boron site and complete occupancy of the metal site was established from structure refinements. The results obtained demonstrate that the use of the `zero-matrix' effect provides considerably increased precision in determining the structural parameters of atoms in hexaborides when studied by neutron diffraction.

The crystal structure of Ce1 - xLax11B6 solid solutions for various x has been studied by high-resolution powder neutron diffraction. A correction for the effect of primary extinction was applied to integrated intensities in a Rietveld program. The refinement results demonstrate good agreement with the data of X-ray single-crystal diffractometer studies performed on the same samples. Vacancies at the boron site and complete occupancy of the metal position are established for all compositions studied. The refined values of the Ce/La ratio at the metal site are in good agreement with those determined by X-ray fluorescence spectrometry on single crystals.

The structural and physical properties of the electron-doped ${\mathrm{Sm}}_{0.1}{\mathrm{Ca}}_{0.9\ensuremath{-}x}{\mathrm{Sr}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}$ perovskite manganites $(0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.8)$ have been studied by combining x-ray and neutron diffractions with measurements of magnetization (in static or pulsed magnetic fields), magnetic susceptibility, and resistivity. A structural change, from $Pnma$ (for $x\ensuremath{\leqslant}0.4$) to $I4∕mcm$ $(0.5\ensuremath{\leqslant}xl0.8)$, is observed at room temperature. A detailed study of two compounds ($x=0.3$ and 0.6), belonging to each structural region, demonstrates different phase separations at low temperature, with mixtures of $C$- and $G$-type antiferromagnetisms associated with different crystallographic structures ($P{2}_{1}∕m$ for $x=0.3$ and $I4∕mcm$ for $x=0.6$). The stabilization of different (crystallographic and magnetic) states together with the different N\'eel temperatures gives the opportunity to control the robustness of the antiferromagnetism versus $A$-site size parameters, such as $⟨{r}_{A}⟩$ and ${\ensuremath{\sigma}}^{2}$. Since $50\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ are not sufficient to collapse the antiferromagnetism in ${\mathrm{Sm}}_{0.1}{\mathrm{Ca}}_{0.3}{\mathrm{Sr}}_{0.6}\mathrm{Mn}{\mathrm{O}}_{3}$, a spontaneous magnetization is observed for $xl0.2$. It is demonstrated that, also in ${\mathrm{Mn}}^{+4}$-rich manganites, the magnetoresistive properties can be optimized by chemical pressure, the Sr for Ca substitution increasing the octahedra tilting in the $Pnma$ structure.

Structural investigations (neutron diffraction and electron microscopy), as well as data on resistance, magnetization, and second harmonic of magnetization, are presented for $^{154}\mathrm{Sm}_{0.5}{\mathrm{Sr}}_{0.5}\mathrm{Mn}{\mathrm{O}}_{3}$ manganite. The neutron diffraction studies reveal a structural phase transition at ${T}_{\mathit{st}}\ensuremath{\approx}135\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ from a high-temperature $Pbnm$ space group to a mixture of two $Pbnm$ phases, which are coherently coupled by atomic positions but differ in cell parameters. Above ${T}_{\mathit{st}}$, this compound is a paramagnetic insulator. At room temperature, a strained and complex nanostructure state is observed in the high-resolution electron microscopy images. In the $Pbnm$ structure it is generated by the coexistence of twinning domains and a small deviation from orthorhombicity for a monoclinic structure. Below ${T}_{\mathit{st}}$, both structural phases begin to exhibit coherent Jahn-Teller distortions, which are different in the two phases. The structural transition is accompanied by the development of a magnetic ordering, so that the ground state is a mixture of ferromagnetism (F) and $A$-type antiferromagnetism (AF-$A$). The AF-$A$ order develops in the new low-temperature structural phase II, whereas the F moment is related to the high-temperature structure I. The several variants of the magnetic ordering are considered for phase I. A more physically justified scenario is that this phase does not possess an AF-$A$ component and exhibits F ordering with an F moment of $1.9(1)\phantom{\rule{0.3em}{0ex}}{\ensuremath{\mu}}_{B}∕\mathrm{Mn}$ at $1.5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. In this case, the AF moment of phase II is found to be $4.1(1)\phantom{\rule{0.3em}{0ex}}{\ensuremath{\mu}}_{B}∕\mathrm{Mn}$ at $1.5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. This unexpected result is attributed to the formation of ferromagnetic polarons in connection with a new electronic structure proposed for the AF-$A$ state. A metalliclike behavior is only observed below $50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and is related to the F phase. The AF-$A$ phase is expected to be insulating. It can exhibit a short-range charge ordering that is observed by electron diffraction at $92\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. A field hysteresis of the second harmonic is found above ${T}_{C}\ensuremath{\sim}{T}_{N}\ensuremath{\approx}{T}_{\mathit{st}}$, which is associated with AF-$A$ regions in the paramagnetic matrix which possess a weak ferromagnetism.

In order to investigate the paramagnetic ground state of the colossal magnetoresistance (CMR) Sm 0 . 5 5 Sr 0 . 4 5 MnO 3 compound we have used a wide set of techniques magnetoresistance, magnetization, high-resolution neutron diffraction, small-angle neutron diffraction, and muon spin relaxation. According to these measurements the paramagnetic ground state would consist of ∼0.8 nm ferromagnetic clusters embedded in a short-range charge/orbital ordered matrix. The CMR effect occurs due to percolation of these ferromagnetic clusters.

Structural neutron diffraction investigations as well as data on resistance, linear susceptibility, and second harmonic of magnetization are presented for ${}^{154}{\mathrm{Sm}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{MnO}}_{3}$ manganite. The structural studies reveal the unique Jahn-Teller (JT) character of this compound which is established to exhibit a $\mathrm{Pbmn}$ space group. Unusual large coherent JT distortions are found to develop below ${T}_{\mathrm{JT}}\ensuremath{\approx}180 \mathrm{K}$ and remain even in a metallic ferromagnetic phase below the Curie point ${T}_{c}\ensuremath{\approx}120 \mathrm{K}$. In the paramagnetic region the resistance is consistent with polaron hopping. A field hysteresis of the second harmonic is observed above ${T}_{c}.$ This evidences the existence of the macroscopic ferromagnetic regions in the paramagnetic matrix. In contrast, temperature dependence of the linear susceptibility reveals a plateau at $Tg{T}_{c}.$ These conflicting peculiarities of the magnetic properties can be explained by assuming the ferromagnetic behavior to be associated with the antiferromagnetic regions possessing a weak ferromagnetism. The ordered regions appear as a result of first order transition at $T\ensuremath{\approx}160 \mathrm{K},$ destroy at ${T}_{*}\ensuremath{\approx}137.5 \mathrm{K}$ and reveal a characteristic three-critical behavior for $\stackrel{\ensuremath{\rightarrow}}{T}{T}_{*}+0$. Change in a balance between the ferromagnetic double exchange hopping of ${e}_{g}$ electrons and the antiferromagnetic interactions of ${t}_{2g}$ spins, which caused by the cooperative JT effect, and the charge ordering correlations are supposed to account for the anomalous magnetic behavior above ${T}_{c}.$

Investigations made by neutron diffraction experiments on the TbTiSi compound are reported. This compound crystallizes in the tetragonal structure of the CeFeSi-type (space group, P 4/ nmm , No. 129). It has an antiferromagnetic transition in the temperature range 180–300 K. The magnetic structure consists of Tb ferromagnetic (001) layers antiferromagnetically coupled along the c axis in the sequence. (0, 0, M z )–(0, 0, M z )–(0, 0, − M z )–(0, 0, − M z ) in the temperature range 2–180 K and at 2 K, M z =8.70(6) μ B . In this compound, no local moment was detected on the Ti site.

We present the electronic, structural and magnetic phase diagram of the colossal magnetoresistive Sm1-xSrxMnO3 (0.16≤x≤0.67) perovskite manganites, constructed on the basis of their regular investigations by high-resolution neutron powder diffraction, temperature magnetic and transport measurements. It is shown, that a real pattern of the physical phenomena in Sm-Sr manganites is considerably more various and is interesting than it was followed from macromeasurements. The tendency of researched system to formation of the phase-separated states on crystallographic as well as, in the even greater extent, on magnetic level is demonstrated. It is shown that there is a clear correlation between fine specific features and temperature evolution of crystal structures and the corresponding types of low-temperature magnetic ordering.

The temperature dependence of the structure of the high temperature superconducting ceramic SmBa 2 Cu 3 O 7 with T c =92 K was investigated in the temperature range from 1.5 K to 300 K, using neutron diffraction measurements on a powder sample with the MiniSfinks, D2B and DMC diffractometers. The sensitivity of the experiment for the oxygen and barium substructures was increased by using a mixture of 152 Sm, 154 Sm and 63 Cu isotopes. The role of bounds such as Cu-O, of CuO 2 and Ba-O plane distortions, order-disorder phenomena due to oxygen as well as the possibility that Sm exists in a mixed valence state, are discussed.

This report will try to present some confirmation of the direct relation between structural peculiarities and physical/chemical properties (oxidation efficiency) by the example of two model systems: CuCr2−xCoxO4+nCuO (carrier) and TiO2 (carrier)+nCuO. More correct crystal structure for Cu(Cr/Co)2O4+nCuO system is proposed.

Neutron powder diffraction experiments on 154 Sm 0.6 Sr 0.4 MnO 3 in the temperature range from 1.5 to 300 K have been performed using the high-resolution G4.2 (LLB, France) diffractometer. The material undergoes an insulator–metal transition at T ∼120 K and exibits the giant magnetoresistance effect. The Jahn–Teller transition temperature is found to be close to 180 K. The temperature dependence of microstrain parameters related to anisotropic peak broadening is obtained. Magnetic scattering detected for T

The crystal and magnetic structures of the manganite 152Sm0.45Sr0.55MnO3 have been established by high resolution neutron powder diffraction. These data are compared with the magnetic and transport properties of this compound. Firstly, it is found that this manganite crystallizes in a perovskite-like structure belonging to the orthorhombic system (Pnma) in the entire temperature range under study (1.5–260 K). Secondly, this study reveals that the magnetic and electronic ground states of 152Sm0.45Sr0.55MnO3 at low temperatures correspond to a homogeneous A-type antiferromagnetic insulator (TN~180 K) with dx2−y2 type orbital ordering. The lack of magnetoresistance for this composition is explained by the lack of coexisting magnetic phases involving ferromagnetism, in contrast to what is observed for the magnetoresistive Sm1−xSrxMnO3 compounds, that is with x≤0.52.

The molecular crystal structures of 3-amino-4-nitro-6-mefhyl-8-oxopyrazolo[1,5-a]pyrimidine (C7H7N5O3; space group P21/n; Z = 4; a = 18.920(4) Å, b = 8.441(2) Å, c = 5.210(1) Å, β = 90.82(2)°) and 3-amino-4-nitro-6,8-dimethylpyrazolo[1,5-a]pyrimidine (C8H9N5O2; space group P[unk]; Z = 2; a = 7.643(2) Å, b = 9.142(3) Å, c = 7.492(1) Å, α = 111.12(2)°, β = 100.66(2)°, γ = 102.58(2)°) have been determined from X-ray and neutron powder diffraction data using grid search procedure. The hydrogen-bonded molecules of the former compound form chains directed along the diagonals of the bc plane, while the latter crystal structure adopts dimeric arrangement.

The NaNO$_{2}$ nanocomposite ferroelectric material in porous glass was studied by neutron diffraction. For the first time the details of the crystal structure including positions and anisotropic thermal parameters were determined for the solid material, embedded in a porous matrix, in ferro- and paraelectric phases. It is demonstrated that in the ferroelectric phase the structure is consistent with bulk data but above transition temperature the giant growth of amplitudes of thermal vibrations is observed, resulting in the formation of a "premelted state". Such a conclusion is in a good agreement with the results of dielectric measurements published earlier., Comment: 4 pages, 4 figures

Vacancy-related defects introduced into n-Si during annealing or aluminium diffusion at high temperature (1000–1250°C) have been studied. Different ambients (argon, nitrogen, vacuum and chlorine-containing atmosphere) were used to create a vacancy supersaturation during heat treatments. Three deep-level centers whose formation is governed by the presence of vacancies have been identified. They were characterized by the following temperature dependences of the thermal emission rate:e3 = 7.92 × 107T2 × exp(− 0.455/kT),e5 = 2.64 × 106T2 × exp( − 0.266/kT),e7 = 7.26 × 106T2 × exp (− 0.192/kT). The influence of different factors, such as heat-treatment conditions, concentration of oxygen and doping level in initial crystals, on center formation was studied. An asymmetric diffuseγ-ray scattering was observed near the surface of a crystal irradiated by thermal neutrons and annealed in a chlorine-containing atmosphere. This scattering is related to the formation of structural defects of the vacancy type. In the same region of the crystal, the concentration of the E7 center was one order of magnitude higher than that of other deep-level centers. Comparison of theγ-ray diffraction and deeplevel transient spectroscopy (DLTS) data suggests that the formation of the center occurs under the conditions of Si supersaturation with vacancies.

The rich and peculiar macro- and microscopic phenomenology observed in the electron-doped region of the Sm-Ca phase diagram of manganites can he found in the unique and fascinating compound Sm 0 . 1 5 Ca 0 . 8 5 MnO 3 . We report the existence of nano- and microscopic phase segregation above and below T N 112 K. The very different nature of the coexisting phases and the field and temperature dependencies are explained considering the interplay of magnetic and structural correlations, which give rise to different structural and magnetic ground states, close in energies (P-Pnma, G+F-Pnma, G-Pnma, C-P2 1 /m).