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Vibrational spectra of NH[sub 4]I have been studied by means of incoherent inelastic neutron scattering at pressures up to 10 GPa using a high-pressure cell of the "toroid" type with tungsten carbide anvils. Librational (L) and transverse optical (TO) mode frequencies as a function of pressure were obtained. The observed behavior of these modes may be explained in terms of their hybridization at pressures P > 6 GPa. A change of dynamics of NH[sub 4]I due to this effect is a possible mechanism for the phase transition which occurs in this system at high pressure. [ABSTRACT FROM AUTHOR]

The crystal structure and vibrational spectra of cation-deficient nanostructured zinс ferrite Zn 0.34 Fe 2.53 ☐ 0.13 O 4 (where ☐ denotes the cation vacancies) have been studied using X-ray diffraction and Raman spectroscopy methods in the pressure range of 0–34 GPa. Our results indicate a phase transition from the initial cubic phase with space group Fd 3 ‾ m to a high-pressure phase with orthorhombic symmetry of Bbmm at pressures above 18 GPa. This phase transition is accompanied by changes in lattice parameters, unit cell volume, interatomic bond lengths, and vibration mode frequencies. [ABSTRACT FROM AUTHOR]

Highlights • The magnetic properties of ordered double perovskite Pb 2 FeSbO 6 were studied in details. • Unexpected long-range antiferromagnetic ordering in Pb 2 FeSbO 6 compound was found. • The antiferromagnetic phase in Pb 2 FeSbO 6 formed on the cation disordering structural domains. • The propagation vector of the antiferromagnetic phase is q = (½, ½, 0). • Under cooling, the structural phase transition in Pb 2 FeSbO 6 occurs. Abstract The structural and magnetic ordering of Pb 2 FeSbO 6 was studied by means of Mössbauer spectroscopy and neutron powder diffraction in the temperature range from 5 to 300 K. The structural phase transition from the initial cubic phase Fm 3 ¯ m to the tetragonal I 4 / m phase was observed in temperature range 170–190 K. The antiferromagnetic order with a propagation vector q = (½, ½, 0) was found at temperature T < T N = 30 K. The temperature dependences of the hyperfine parameters of Mössbauer spectra and magnetic moments for Pb 2 FeSbO 6 at low temperatures were obtained. The relationships between the short-range cation ordering observed by Mossbauer spectroscopy and the long-range cation ordering observed by neutron powder diffraction are discussed. [ABSTRACT FROM AUTHOR]

• Suppression of the low temperature cone structure under pressure. • Rapid pressure-induced increase of the lock-in transition temperature. • Significant increase of commensurate q z component of the helical structure up to ¼ c * below the lock-in transition. • Magnetic P-T phase diagram of elemental Ho. The pressure response of the magnetic and structural properties of elemental holmium was explored by means of neutron powder diffraction in the pressure range up to 8.7 GPa and the temperature range 7 – 290 K. At ambient pressure, below T N = 127 K the incommensurate helical state with a propagation vector q = (0 0 q z) is evidenced. On temperature lowering, the q z value decreases from 0.270 c * (at 125 K) to 5/26 c * at T L = 20 K. Below the lock-in transition temperature T L , a commensurate cone structure is formed due to canting of magnetic moments towards the c axis. Upon lattice compression, a gradual suppression of the low temperature cone structure was found and just a helical state was observed above 4 GPa. This state is incommensurate in the temperature range T L < T < T N and becomes commensurate below T L. At T = 7 K, the q z component evolves towards ¼ c * value at 8.7 GPa. The Néel temperature decreases to 108 K with a pressure increase up to 8.7 GPa with a pressure coefficient dT N /dP ≈ −2.2 K/GPa, while the lock-in transition temperature exhibits opposite behavior and grows up to about 50 K with a coefficient of dT L /dP ≈ 3.4 K/GPa. The magnetic P - T phase diagram of Ho is constructed. The compression of Ho lattice at T = 7 K is nearly isotropic, as found from about the same compressibilities of the a and c axes. [ABSTRACT FROM AUTHOR]

Crystalline phosphors made of yttrium aluminum borates YAl 3 (BO 3 ) 4 doped with cerium have been synthesized by colloidal chemical approach involving co-precipitation of precursors from aqueous solutions of the corresponding salts in the presence of boric acid that is followed by heat treatment. Structural phase transitions occurring during the synthesis of YAl 3 (BO 3 ) 4 :Ce 3+ were studied using thermal analysis methods (TG, DTA, and DSC). The crystalline structure and luminescent properties of the synthesized compounds were investigated by the means of X-ray powder diffraction and optical spectroscopy. The decrease in the luminescence intensity and increased splitting of the main term of Ce 3+ ions of YAl 3 (BO 3 ) 4 :Ce 3+ were observed at a higher concentration of the ion-activator of 10 % wt. This observation was attributed to the alteration of the structure of optical centers due to the partial oxidation of Ce 3+ ions into the Ce 4+ state. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of doped ferrite Zn 0.3 Cu 0.7 Fe 1.5 Ga 0.5 O 4 have been studied by means of the neutron diffraction method at high pressures up to 4.7 GPa and in temperature range 300–425 K. By increasing the temperature and the pressure, a gradual suppression of the magnetic moments of iron ions in both A and B crystallographic sites was observed. This effect corresponds to a magnetic phase transition from the ferrimagnetic state to paramagnetic one. The lattice parameters, interatomic bond lengths and angles, magnetic moments of iron ions as functions of temperature and pressure were obtained. Upon compression, the magnetic ordering temperature of studied ferrite decreases with a large pressure coefficient dT c / dP  = −19(1) K × GPa −1 . [ABSTRACT FROM AUTHOR]

The crystal structure and magnetic properties of DyCo 2 compound were studied at pressures p ≤ 5.6 GPa, in the temperature range 4–300 K, by neutron diffraction. In addition, magnetic measurements and band structure calculations were performed. The pressure dependence of the cobalt moments, experimentally determined, agree well with the calculated values. An isomorphic structure transition, parallelly with the collapse of cobalt moments, has been evidenced. The physical mechanisms involved in describing the pressure effects on the DyCo 2 magnetic properties are analysed. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of Cr 2 O 3 have been studied by means of X-ray and neutron powder diffraction at high pressures up to 35 GPa. The lattice compression of the rhombohedral crystal structure of R 3 ¯ c symmetry is slightly anisotropic with anomaly in the pressure behavior of the c/a parameters ratio at P ≈ 20 GPa of presumably magnetic nature. The oxygen octahedra around chromium ions become more symmetric with close values of shared and unshared bonds under high pressure. The antiferromagnetic structure of Cr 2 O 3 remains stable in the studied pressure range up to 35 GPa. The pressure coefficient of the Néel temperature, (1/ T N )( dT N /dP ) = + 0.0091 GPa −1 , is significantly less in comparison with perovskite-like compounds containing Cr 3+ and Mn 4+ ions of similar electronic configuration. [ABSTRACT FROM AUTHOR]

The structural, magnetic and vibrational properties of the BaMn 1- x Ti x O 3 system (0 ≤ x ≤ 0.25) have been studied by X-ray and neutron powder diffraction, electron spin resonance (ESR) and Raman spectroscopy methods. A sequence of the structural phase transitions 15R → 8H → 9R → 10H → 12R was observed upon Ti doping. The structural parameters of the observed phases were determined. Antiferromagnetic ordering in the 15R, 9R and 8H structural phases was observed at low temperatures. The magnetic propagation vector is q = (0 0 1/2) for the 15R and 9R phases and q = (0 0 0) for the 8H phase. The magnetic ordering temperatures and the ordered Mn magnetic moments are suppressed rapidly with increase of the Ti concentration from T N = 230 ( x = 0) to 100 K ( x = 0.25) and m = 2.0 to 1.2 μ B , respectively. The relationship between the Raman spectra of different structural phases of BaMn 1- x Ti x O 3 and concentration dependencies of the vibrational modes were analyzed. [ABSTRACT FROM AUTHOR]

The crystal, magnetic structure and vibrational spectra of multiferroic GaFeO 3 have been studied by means of neutron, X-ray powder diffraction and Raman spectroscopy at pressures up to 6.2 and 42 GPa, respectively. A presence of Fe/Ga antisite disorder leads to a formation of the ferrimagnetic ground state with the Néel temperature T N = 292 K at ambient pressure. Upon compression, the magnetic ground state symmetry remains the same and the Néel temperature increases with a pressure coefficient (1/T N )(dT N /dP) = 0.011(1) GPa −1 . Application of high pressure above 21 GPa leads to a gradual structural phase transition from the polar orthorhombic Pc 2 1 n phase to nonpolar orthorhombic Pbnm phase. It is accompanied by anomalies in the pressure behaviour of several Raman modes. Pressure dependencies of lattice parameters and Raman modes frequencies in the observed structural phases were obtained. [ABSTRACT FROM AUTHOR]

• A significant suppression of the ordered magnetic moment at high pressure is observed, associated with enhancement of spin fluctuations. • The pressure increase of Neel temperature is more pronounced with respect to other hexagonal RMnO 3 compounds. • A change of the ground magnetic state symmetry from mixed Г 1 + Г 2 to pure Г 1 irreducible representation is expected at pressure of about 6 GPa. The crystal and magnetic structures of hexagonal manganite ScMnO 3 have been studied by means of neutron diffraction at high pressures up to 2 GPa in the temperature range 10–300 К. At ambient pressure below T N = 130 K the triangular antiferromagnetic (AFM) state of mixed Г 1 + Г 2 irreducible representation is formed. Upon application of high pressure, the symmetry of magnetic structure persists up to 2 GPa. A significant suppression of the ordered magnetic moment and gradual spin reorientation were revealed under pressure. The baric dependence of Neel temperatures T N was obtained with the average linear pressure coefficient dT N / d P = 6.9 K/GPa, which is significantly larger with respect to related compounds like YMnO 3. For the data obtained, one may expect modification of the magnetic ground state symmetry to the pure Г 1 representation at pressures about 6 GPa. [ABSTRACT FROM AUTHOR]

The crystal and magnetic structure of a manganite La 0.7 Sr 0.3 Mn 0.83 Nb 0.17 O 3 have been studied by means of a neutron diffraction method at pressures up to 4.5 GPa and in temperature range 4–290 K. At ambient pressure and temperature below T C = 150 K a ferromagnetic FM state is stabilized in this compound. At pressures P ≥ 1.5 GPa and temperature below T N ∼110 K appearance of a new A-type antiferromagnetic AFM phase in La 0.7 Sr 0.3 Mn 0.83 Nb 0.17 O 3 has been observed. A further pressure increasing leads to an increase in the volume fraction of the A-type antiferromagnetic AFM phase, which coexists with the suppressed ferromagnetic phase in the whole experimental pressure range. The Curie and Néel temperature increase upon lattice contraction with comparable pressure coefficients dT C /dP = 2.1 K/GPa and dT N /dP = 1.6 K/GPa. The structural mechanisms of the changes in magnetic structure of La 0.7 Sr 0.3 Mn 0.83 Nb 0.17 O 3 manganite are discussed. [ABSTRACT FROM AUTHOR]

La0.7Ca0.3Mn0.5Fe0.5O3(LCMFO) ceramic samples were prepared by conventional solid-state reaction. X-Ray diffraction investigations show that samples have orthorhombic space group Pnma (a = 5.447(2) Ǻ, b = 7.709(3) Ǻ, c = 5.467(3) Ǻ). During the neutron powder diffraction measurements of LCMFO in the temperature range of 10 ÷ 300 K the antiferromagnetic long-range ordering of G-type was seen. It has been established that 50% substitution of Mn/Fe leads to a complete suppression of the ferromagnetism in LCMFO samples. Investigations of temperature dependence of the magnetization, M(T), suggests the frustration of magnetic ground state and the existence of a spin-glass or a cluster-glass phase below the magnetic transition temperature close to 350 K. The temperature dependences of conductivity for La0.7Ca0.3Mn0.5Fe0.5O3sample investigated in magnetic fields B = 0 and 1 T. According to the research, the mechanisms of hopping conductivity were established. Micro parameters in density of localized states were calculated for LCMFO samples. The width of the Coulomb gap Δ = 0.67 eV, rigid gap δ = 0.324 eV and the localization radii of charge carriers were estimated. [ABSTRACT FROM PUBLISHER]

• Formation of complex modulated commensurate states under pressure. • Suppression of temperature range of intermediate incommensurate magnetic states under pressure. • Positive pressure coefficients of Néel and lock-in transition temperatures. The magnetic and structural properties of elemental thulium were studied by means of neutron powder diffraction at pressures up to 5.5 GPa in the temperature range 7 – 290 K. At ambient pressure below T N = 52 K, the incommensurate magnetic state with a longitudinal sinusoidal modulation and propagation vector q = (0, 0, q z) was formed. The q z value increases on cooling from 0.279(2) and reaches the commensurate value of 2/7 at the temperature T 1 = 24 K. The new magnetic arrangement is of an antiphase domain structure, composed of structural blocks involving three or four hexagonal layers with magnetic moment directions parallel within a given block and oppositely alternating from block to block along the c axis. Under high pressure, the T N value increases slightly up to 57 K at 5.5 GPa with a pressure coefficient dT N /dP = 0.9 K/GPa. The pressure dependence of the T 1 temperature is more pronounced with a pressure coefficient dT 1 /dP = 2.9 K/GPa. The arrangement of commensurate magnetic structures formed below T 1 is strongly pressure dependent. A formation of the complex magnetic states composed of structural blocks involving three or four hexagonal layers with magnetic moment signs alternating from block to block along the c axis with q z = 7/23 at 2 GPa and q z = 7/22 at 5.5 GPa was observed. The lattice compression of Tm at T = 7 K demonstrates a weak anisotropy with the most compressible c axis. [ABSTRACT FROM AUTHOR]

The crystal and magnetic structure of nanostructured manganites La 0.63 Sr 0.37 MnO 3 and La 0.72 Sr 0.28 MnO 3 has been studied by means of a neutron diffraction method in the pressure range 0–4.5 GPa and the temperature range 5–300 K. In both samples the FM ordering is formed close above the room temperature and at cooling below T < 270 K the ferromagnetic FM phase coexists with an A-type antiferromagnetic AFM phase. At high pressures the volume fraction of AFM phase increases, while FM is gradually suppressed. The structural aspects of the magnetic phase separation and pressure effects on the studied nanostructured manganites are discussed. [ABSTRACT FROM AUTHOR]

The Ca 1.5 La 0.5 FeMo 1 − x W x O 6 double perovskites with x ⩽ 0.3 crystallize in a monoclinic structure having space group P2 1 /n. The degree of crystallographic ordering is increased as the tungsten content is higher. As a result, there is an increase of both saturation magnetizations and Curie temperatures. The magnetic susceptibilities follow temperature dependences typical for a ferrimagnetic system. The valence states of iron and molybdenum ions as well their distributions in the lattice sites were determined. These data were correlated with magnetic and transport properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] The detailed P–T phase diagram of BiMnO3 was established. [•] We found three monoclinic modifications of BiMnO3 at pressure and temperature. [•] A suppression of monoclinic C2/c phase have been observed under pressure. [•] We found a new orthorhombic Imma phase of BiMnO3 at P >20GPa. [Copyright &y& Elsevier]

Highlights: [•] Evolution with pressure and temperature of holmium and cobalt moments. [•] Correlation between cobalt moments and exchange field. [•] Band structure calculations. [•] Analysis of cobalt magnetism in spin fluctuations model. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure and magnetic properties of TbCo2 compound have been analyzed by neutron diffraction, at pressures up to 4.1GPa in the temperature range 10–300K. A rhombohedral type structure of type is shown below Curie temperature. The distortion degree of structure increases with pressure as well as when lowering temperature. The temperature dependences of terbium and cobalt moments can be described by Brillouin functions. The Curie temperatures decrease linearly with pressure with a slope of dTc /dP =−9K/GPa. The evolution with pressure of the cobalt magnetic moments and Tb5d band polarizations are theoretically analyzed. The experimental data are well described by band structure calculations. The magnetic behavior of cobalt in heavy rare-earth RCo2 compounds is analyzed in spin fluctuations model. A gradual quenching of spin fluctuations by internal field was shown. [Copyright &y& Elsevier]

Abstract: Measurements of spin-lattice relaxation time T 1 for resorcinol have been made by the proton NMR technique using the saturation method in the temperature range 280–380K and pressure up to 800MPa. The pressure-induced α–β transition evolved through two phase coexistence range was observed. The crystal structure and vibrational spectra of the resorcinol have also been studied by means of X-ray diffraction and Raman spectroscopy at pressures up to 19GPa in temperature range 290–380K. In experiments with a rapid pressurization rate, suppression of α–β polymorphic transition in resorcinol occurs. In experiments with a slow pressurization rate, two structural phase transitions, between orthorhombic α and β phases at P =0.4GPa and from β to another orthorhombic γ phase at P =5.6GPa, were observed. At pressures above 12.5GPa, a gradual transformation to the amorphous phase was revealed. The lattice parameters, unit cell volumes and vibration modes as functions of pressure and temperature were obtained for the different polymorphic modifications of resorcinol. [Copyright &y& Elsevier]

The crystal and magnetic structures of hexagonal manganites YMnO3 and LuMnO3 have been studied by powder neutron diffraction up to 6 GPa in the temperature range of 10-300 K. At ambient pressure, a triangular antiferromagnetic (AFM) state of a Γ1 irreducible representation is stable below TN=70 K in YMnO3. Upon application of high pressure, a spin-reorientation was observed and the triangular AFM structure evolves from Γ1 to Γ1+Γ2 representation symmetry. In LuMnO3, the triangular AFM state of a Γ2 symmetry with TN ≈ 95 K remains stable in the investigated pressure range. The ordered Mn magnetic moment is suppressed at high pressure and low temperature, with much more pronounced effects for YMnO3, indicating enhanced spin fluctuations due to stronger magnetic frustration of the triangular lattice under higher pressure. The relationship between the evolution of spin fluctuations and in-plane Mn-O bonds under pressure is analyzed. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure and vibrational spectra of deuterated pyridinium perrhenate (d5PyH)ReO4 (C5D5NHReO4) have been studied by means of X-ray diffraction and Raman spectroscopy at high pressures up to 15 and 9.5GPa, respectively. Two phase transitions, from orthorhombic phase II with Cmc21 symmetry to phase I with Cmcm symmetry at P =0.7GPa and to new monoclinic phase IV with P21 symmetry at P =5GPa were observed. The internal vibrational modes frequencies, lattice parameters and unit cell volume as functions of pressure were obtained for different phases. [Copyright &y& Elsevier]

• A phase coexistence of hcp and Sm-type phases is found in 160Gd at ambient conditions. • The hcp phase and FM order are rapidly suppressed under pressure. • In the Sm-type phase, stabilized by pressure, the AFM order is formed. Structural and magnetic properties of the isotopically substituted 160Gd metal (97.5 % enrichment) were studied by means of neutron powder diffraction at pressures up to 9 GPa in the temperature range 7 – 290 K. At ambient conditions, a coexistence of hexagonal close packed (hcp) and Sm-type rhombohedral phases was observed. Under high pressure, the hcp phase was suppressed gradually and above 6 GPa only the Sm-type phase is observed. The long range ferromagnetic order formed in the hcp phase is also suppressed rapidly with a pressure coefficient of the Curie temperature dT C /dP = -6.3(1) K/GPa. In the Sm-type phase below the Néel temperature of about 100 K (evaluated for 9 GPa), the long range antiferromagnetic order with a propagation vector k AF = (0 0 1/2) is formed. The lattice parameters and unit cell volume as functions of pressure in the hcp and Sm-type phases were determined. A partial phase transformation of the Sm-type phase to the double hexagonal close packed (dhcp) phase was observed at 9 GPa. [ABSTRACT FROM AUTHOR]

Abstract: The structure of the deuterated pyridinium perrhenate (d 5PyH)ReO4 (C5D5NHReO4) was studied by means of powder X-ray diffraction at high pressures up to 3.5GPa at room temperature and neutron diffraction at high pressures up to 2.0GPa in the temperature range 10–300K. At ambient conditions deuterated pyridinium perrhenate has orthorhombic structure of the Cmc2 1 symmetry (ferroelectric phase II). At T <250K a phase transition to the orthorhombic phase of the Pbca symmetry (paraelectric phase III) was observed. At P >0.7GPa the phase transition to orthorhombic phase with the Cmcm symmetry (paraelectric phase I) was observed at ambient temperature. At P =2GPa the phase I is stable in the temperature range 10–293K, indicating a suppression of the ferroelectricity in (d 5PyH)ReO4 by application of high pressure. P–T phase diagram of (d 5PyH)ReO4 at high pressures up to 2GPa is discussed. [Copyright &y& Elsevier]

The magnetic and crystal structures of anion-deficient La0.7Sr0.3MnO3− d manganites ( d = 0.15 and 0.20) are studied by neutron diffraction in the range of high pressures 0–5 GPa and temperatures 10–300 K. It is found that a spin-glass state forms in La0.7Sr0.3MnO2.85 below T g ∼ 50 K, while magnetic phase separation is observed in La0.7Sr0.3MnO2.80, which is characterized by the coexistence of AFM domains of the C type with spin-glass domains. As distinct from the stoichiometric A0.5Ba0.5MnO3 manganites (A = Nd, Sm), in which the high-pressure effect suppresses the spin-glass state and gives rise to ferromagnetism, the spin-glass state in La0.7Sr0.3MnO2.85 is stable under pressure. The bulk modulus of La0.7Sr0.3MnO2.85 is considerably smaller than that for the stoichiometric La0.7Sr0.3MnO3 compound. The causes of the formation of different types of the magnetic structure in La0.7Sr0.3MnO3− d ( d = 0.15 and 0.20) and different high-pressure effects on the magnetic structure of stoichiometric and anion-deficient manganites are analyzed. [ABSTRACT FROM AUTHOR]

The crystal and magnetic structures of the orthoperovskite Pr0.8Na0.2MnO3 with non-integral mean valence (Mn3+/Mn4+) have been studied by means of powder neutron diffraction up to high-quasi-hydrostatic pressure of 4.6 GPa. At normal conditions, the system undergoes a charge ordering transition at TCO=215 K, followed by an antiferromagnetic arrangement of the pseudo-CE type at TN=175 K. Under high external pressures, a microscopically separated state is formed, consisting of a mixture of the A-type AFM phase (TN∼155 K) and metastable FM regions (TC∼175 K). A possible reason for the appearance of the A-type AFM phase is the compression anisotropy which leads to marked apical contraction of MnO6 octahedra under high pressure and creates favorable conditions for appearance of the d(x2−y2) orbital polarization, prerequisite for the A-type AFM order. It is argued that the pressure-induced structural changes in Pr0.8Na0.2MnO3 are accompanied by an insulator–metal transition. [Copyright &y& Elsevier]

A crystal and magnetic structure of manganites Pr 0.7 Ca 0.3 Mn 1- y Fe y O 3 ( y  = 0, 0.1) has been studied by means of powder neutron diffraction at pressures up to 4 GPa in the temperature range 15-300 K. Under high pressure, an appearance of A-type antiferromagnetic state in both systems was observed. Both compounds exhibit anisotropic compression of the lattice which leads to the apical compression of MnO 6 octahedra along the crystallographic b -axis. The calculated from obtained structural data pressure dependence of the charge-carrier bandwidth is in a qualitative agreement with observed pressure behavior of insulator-metal transition temperature within the framework of the double-exchange model. [ABSTRACT FROM AUTHOR]

The crystal and magnetic structure of the nanostructured manganite La 0.53 Sr 0.47 MnO 3 has been studied using the neutron diffraction method in the pressure range 0–5.5 GPa and the temperature range 15–300 K. At ambient pressure, the ferromagnetic ordering in the studied compound is formed below T ≈ 335 K. With an increase of the pressure above 2.1 GPa and cooling below T < 250 K, an A-type antiferromagnetic phase appears, which coexists with the initial ferromagnetic one. Further increase of the pressure leads to the growth of the volume fraction of the antiferromagnetic phase, while the ferromagnetic ordering is gradually suppressed. The structural origins of the pressure-induced magnetic phase separation in the nanostructured manganites are discussed. • The structure of nanomanganite La0.53Sr0.47MnO3 at high pressure have been studied. • The FM ordering in this compound was formed at ambient pressure, below T ≈ 335K. • At P ≥ 2.1 GPa and T < 250 K, the coexistence of FM and A-type AFM phase was found. • The structural separation was discussed in the framework of the "core-shell" model. • The most important parameters of crystal and magnetic structures were calculated. [ABSTRACT FROM AUTHOR]

Abstract: At the experimental station “Mediana” of the Kurchatov Synchrotron Radiation Source, a diffractometer for investigations of microsamples with the help of synchrotron radiation has been created. The design and basic parameters of the diffractometer are described. The results of experiments carried out with the powder diffractometer are presented. [Copyright &y& Elsevier]

The vibrational spectra of the ranitidine hydrochloride have been studied using Raman spectroscopy at pressures up to 11.2 GPa. At a pressure above 1.2 GPa a polymorphic phase transition from the initial form II to a new pressure induced form V has been observed. The vibration modes of the ranitidine hydrochloride as functions of pressure have been obtained. At pressures above 6.2 GPa, a gradual transformation to the amorphous phase of ranitidine hydrochloride has been revealed. Image 1 • The Raman spectra of ranitidine hydrochloride at high pressure were measured. • The new pressure induced phase of ranitidine hydrochloride has been found. • The pressure driven amorphization of ranitidine hydrochloride has been observed. • The anomalies in the baric dependencies of vibration modes were obtained. [ABSTRACT FROM AUTHOR]

• Magnetically disordered phase is suppressed under pressure. • The Néel temperature increases substantially under pressure. • The mechanism of next nearest neighbor superexchange interactions of A-O-O-A type is proposed. The crystal and magnetic structures of the frustrated Co 3 O 4 spinel oxide have been studied by means of neutron diffraction at high pressures up to 8.7 GPa in the temperature range 5–300 K. At ambient pressure, a coexistence of the long range ordered antiferromagnetic (AFM) phase and short range disordered phase below T N = 33 K was observed. At pressures above 2 GPa, a suppression of the magnetically disordered phase and stabilization of the AFM phase, characterized by rapid increase of the Néel temperature in 1.5 times from 33 to 51 K with a pressure coefficient dT N /dP = 2.1 K/GPa occur. The observed phenomena are analyzed in terms of the competing nearest neighbor and next nearest neighbor magnetic interactions. In addition to the A-O-B-O-A nearest neighbor superexchange, an important role of the A-O-O-A next nearest neighbor superexchange interactions in magnetic behavior of Co 3 O 4 is pointed out. [ABSTRACT FROM AUTHOR]

• Structural anomalies at 20 GPa bring indirect evidence of insulator-metal transition. • The Néel temperature of TbBaCo 1.91 Fe 0.09 O 5.5 is reduced substantially under pressure. • The ferromagnetic component of the magnetic structure is suppressed under pressure. • A tendency towards decrease of the ordered Co/Fe magnetic moments is observed. The crystal and magnetic structures of the perovskite-like, oxygen deficient layered cobalt oxide TbBaCo 1.91 Fe 0.09 O 5.5 have been studied by means of neutron diffraction at high pressures up to 6.2 GPa in the temperature range 5–300 K and X-ray diffraction at high pressures up to 30 GPa and ambient temperature. The structural anomalies in lattice compression at P = 20–25 GPa were revealed, which could be associated with the insulator-metal transition. At ambient pressure below T N = 300 K a formation of the complex magnetic structure on the Co/Fe sublattice, comprising the G-type antiferromagnetic (AFM) and ferromagnetic (FM) components, was observed. Below T ≈ 150 K the FM component vanished. At T = 5 K a presence of the long range AFM order on the Tb sublattice was also revealed. At high pressures, the FM component has become suppressed and the only G-type AFM order was found for the Co/Fe sublattice. The Néel temperature decreased noticeably down to 275 K at P = 6.2 GPa with a pressure coefficient dT N / dP = −4 K/GPa. The intrinsic mechanisms of the observed pressure-induced magnetic phenomena are discussed. [ABSTRACT FROM AUTHOR]

The high-pressure evolution of structural and magnetic properties of the single valence Mn3+ manganite La 0.8 Sr 0.2 Mn 0.9 Sb 0.1 O 3 was studied by means of neutron powder diffraction up to 4.5 GPa in the temperature range of 10–300 K. At ambient pressure, a ferromagnetic ground state with the magnetic ordering temperature T C ≈ 175 K is stabilized. Application of high pressure suppresses the initial FM phase and leads to the appearance of a new A-type antiferromagnetic AFM phase with T N ~ 130 K at P = 2.2 GPa. Under compression, both T C and T N almost linearly increases with the pressure coefficient of 1.9(2) and 0.9(3) K/GPa, respectively. It is assumed that the appearance of the A-type AFM state is mediated by the strong anisotropic distortions of MnO 6 octahedra, coupled to the e g d x 2 - z 2 orbital polarization at high pressures. [ABSTRACT FROM AUTHOR]

We report a systematical investigation of the structural, magnetic, electronic, and dielectric properties of BaFe 1- x Ti x O 3- δ (x = 0.05, 0.10, 0.15 and 0.20) samples synthesized via the solid-state reaction method. Rietveld refinement using a combination of room-temperature X-ray (XRD) and neutron powder diffraction (NPD) data confirms single phases with a 6H-type structure for all the samples. X-ray absorption spectroscopy (XAS) study reveals a coexistence of Fe3+ and Fe4+, whose ratio remains almost unchanged with increasing Ti concentration. Magnetization measurements reveal a low-temperature inhomogeneous magnetic state with coexisting ferromagnetic (FM), AFM clusters and a paramagnetic phase. Moreover, magnetization of x = 0.10 shows a pinched hysteresis loop behavior, suggesting the coexistence of hard and soft FM phases in samples with high Ti concentrations. Low-temperature NPD measurements also confirm the absence of any long-range magnetic order in the samples. A colossal dielectric permittivity and two relaxation processes are observed for most of the studied samples. There is a change in electric conduction mechanism from the small polaron hopping to the Mott's variable-range hopping with increasing Ti concentration. • 6H-type Ti-doped BaFeO 3- δ exhibit colossal dielectric permittivity. • Interfacial Maxwell-Wagner polarization effect at grain boundaries is the origin of the colossal dielectric permittivity. • Change in the electrical conduction mechanism upon increasing Ti-doping level. • Ti doping destroys the helical antiferromagnetic long-range order of the undoped BaFeO 3. • Complex inhomogeneous magnetic state with coexistence of cluster-glass and paramagnetic phases. [ABSTRACT FROM AUTHOR]

The crystal structure and magnetic properties of YCo 4 B intermetallic compound were studied by means of neutron diffraction at pressures p ≤ 6.5 GPa. No structural transitions are evidenced. The cobalt moments at 2c and 6i sites decrease, upon lattice compression, with a rate dlnM Co /dp ≅ 0.11 GPa−1, showing a rather high degree of itinerancy. The evolutions with pressure of band structures have been also analysed and the computed cobalt moments are discussed in correlation with those experimentally determined. • Pressure dependence of the crystal structure of YCo 4 B as determined by neutron diffraction at p ≤ 6.5 GPa. • Pressure dependences of the cobalt moments at 2c and 6i sites. • Electronic band structures and their evolution with pressure as well as of computed cobalt moments. • Collapse of the cobalt moments at p = 8.8 ± 0.4 GPa. [ABSTRACT FROM AUTHOR]

The structure of ternary mercury chalcogenides HgSe[sub 1-x]S[sub x] (x = 0.3, 0.5, 0.6) and HgTe[sub 1-x]S[sub x] (x = 0.15) was studied by means of powder neutron diffraction at pressures up to 8 GPa. A phase transition from the zinc blende cubic structure to the hexagonal cinnabar structure was observed at P ≈ 1 GPa in HgSe[sub 1-x]S[sub x] systems and at P ≈ 1.6 GPa in HgTe[sub 0.85]S[sub 0.15]. A coexistence of these two phases was observed in the vicinity to the transition pressure. Lattice parameters and atomic positional parameters for the high-pressure hexagonal phase were determined. [ABSTRACT FROM AUTHOR]

High-pressure neutron-diffraction experiments on the pseudo-ternary compound NdAl[sub x]Ga[sub 2-x] revealed a pressure-induced isostructural phase transition for x = 1.00 and 1.08 above about 1.5 GPa at room temperature. Within its hexagonal AlB[sub 2] structure the compound changes its lattice ratio c/a discontinuously from 0.97 to 0.84 in analogy to chemical pressure for x > 1.12. Pressures up to 5.2 GPa did not result in a pure high-pressure phase but rather in a mixture of both phases. The intermetallic MN[sub 2] phases of the AlB[sub 2] structure are known to appear in two distinct groups with different c/a ratios. The observed isostructural transition is discussed within the framework of near-neighbor diagrams. [ABSTRACT FROM AUTHOR]