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The structural and magnetic properties of mixed compounds Tb1-xYxFe11Mo with x = 0-1.0 have been investigated by means of x-ray diffraction and magnetic measurements. The compounds crystallize in the tetragonal ThMn12-type structure with space group I4/mmm. The lattice parameters a, c and the unit-cell volume V vary slightly with the Y content, since the atomic radius of Y is close to that of Th. The Curie temperature of the compounds increases for x

TbFe12-xMOx compounds (x = 0.5-3.0) with the tetragonal ThMn12-type structure have been synthesized. The structural and the magnetic properties of the compounds have been investigated by means of X-ray diffraction and magnetic measurements. The lattice parameters a, c and the unit-cell volume V increase with increasing Mo content. Both the Curie temperature T-C and the saturation magnetization M-S at 5 K decrease monotonically with increasing Mo content. The molecular field coefficients n(FeFe) and n(RFe) have been estimated from a mean-field analysis of the Curie temperature of the compounds. The easy magnetization direction at room temperature changes with increasing Mo content from planar to probably cone and finally to uniaxial. The decrease of saturation magnetization with increasing Mo content may be caused by the reduction of the mu(Fe) due to hybridization of the Fe and Mo d-bands. (c) 2005 Elsevier B.V. All rights reserved.

The crystal structure and magnetic properties of a series of ordered double perovskite oxides (Sr2−3xLa2xBax)FeMoO6 ( 0 ⩽ x ⩽ 0.3 ) have been investigated. X-ray powder diffraction reveals that the crystal structure of the compounds changes from a tetragonal I4/m lattice to a cubic Fm 3 ¯ m lattice around x = 0.2 . Though the nominal average size of the A site cation of (Sr2−3xLa2xBax)FeMoO6 is designed to be almost independent of x, the refinements of the crystal structure show that the lattice constants increase with x in both the tetragonal and the cubic phase regions due to electron doping. As the x increases, the degree of cationic ordering on the B site is decreased pronouncedly, while the Curie temperature of the compounds is nearly unchanged. The saturation magnetization of the compounds decreases with x and shows a linear dependence on the degree of cation ordering. The resistivity of the parent compound shows a semiconducting behavior below room temperature, but those of the doped samples exhibit a metal–semiconductor transition. A correlation between the resistivity and metal-semiconducting transition temperature (TM−S) is observed. The resistivity and TM−S of the compounds decrease with x for x ⩽ 0.2 and increase for x ⩾ 0.2 . Magnetoresistance of the compounds is reduced by the La/Ba doping. All these observations can be understood based on the interplay of the electron doping, change in bandwidth and the anti-site defect concentration.

Nanometer titanium dioxide (TiO2) films were deposited on muscovite flakes and doped with a number of different metal ions (Al3+, Sn4+, Fe3+, Cu2+, Co2+, Mn2+ or Zn2+) using a chemical liquid deposition method. The morphology and the anatase-rutile (A-R) transformation were studied by scanning electronic microscopy (SEM) and X-ray diffraction (XRD), respectively. Apart from round particles, SEM micrographs show that euhedral pillar rutile grains are found in the samples doped with Fe3+, Mn2+ or Zn2+ ions. The rutile phase of TiO2 thin layers on muscovite could be generated at low temperature, 60 degrees C. The XRD results confirm that the addition of metal ions affects the anatase-rutile (A-R) transformation. The Mn2+, Sn4+, Fe3+ and Zn2+ ions promote the A-R transformation while the Al3+, Cu2+ and Co2+ ions inhibit the A-R transformation of TiO2 thin layers on muscovite. The influence of metal ion doping on the A-R transformation of the TiO2 thin layers on muscovite depends on the substitution of foreign ions for Ti4+ ions in TiO2 thin layers. (c) 2005 Elsevier B.V. All rights reserved.

The YCo5.0-xMnxGa7.0 compounds crystallize with the ScFe6Ga6-type structure. The lattice of YCo5.0-xMnxGa7.0 expands with the increase of the Mn content for 0.05

The crystal structure and magnetic properties of Sm(CO,M)(7) (M = Si, Cu, Ti, Zr, and Hf) compounds with the TbCu7-type structure have been investigated by means of X-ray powder diffraction and magnetic measurements. For the Sm(Co,M)(7) compounds, the formation of the compound is dominated by the enthalpy of formation of Mco(7), atomic radius ratio of Sm to (Co, M) and the electronic configuration of the doping element M, while the site occupation of M is determined by the enthalpies of solution of M in liquid Sm and Co as well as by the electronegativity difference among M, Sm and Co. However, the Sm(Co,Cu)(7) compounds exhibit different stabilizing mechanism, which may be due to the large mutual solubility between Co and Cu in the Sm(Co,Cu)(7). The stabilizing element Si and Cu prefer to occupy the 3g site, whereas Ti, Zr and Hf have preference to occupy the 2e site. Both the saturation magnetization and Curie temperature of the Sm(Co,M)(7) compounds decrease with increasing M content, while the magnetic anisotropy increases with increasing M content. The magnetic anisotropy field is related closely to the content and site occupation of the doping element M, which agrees with the theoretical analysis based on the individual site contribution model. (c) 2004 Published by Elsevier Ltd.

The crystal structure and magnetic properties of (NdxR1-x)(3)Fe24Cr5 (R = Gd and Tb) compounds with x = 0.0-0.8 have been investigated by means of X-ray diffraction and magnetic measurements. All the samples are single phase and crystallize in the Nd-3(Fe,Ti)(29)-type structure with space group A2/m. As the Nd content increases, the lattice parameters a, b, c and the unit-cell volume V increase in both the (NdxGd1-x)(3)Fe24Cr5 and the (NdxTb1-x)(3)Fe24Cr5 compounds due to the lanthanide contraction. The room-temperature easy magnetization direction changes to the [0 4 0] direction with increasing Nd content. The Curie temperature of (NdxGd1-x)(3)Fe24Cr5 decreases monotonically upon substitution of Nd for Gd, while the Curie temperature of the (NdxTb1-x)(3)Fe24Cr5 compounds decreases with the Nd content for x = 0-0.4 and increases for x = 0.4-0.8. The saturation magnetization M-S increases monotonically with increasing Nd content for both compound systems and can be described in terms of a simple dilution model. (c) 2005 Elsevier B.V. All rights reserved.

Tb-doped AlN films are prepared by reactive radio frequency (RF) magnetron sputtering under different work conditions. As the RF power increases from 50 to 250 W, the prepared film changes from amorphous to c-axis oriented crystalline. Lower work pressure and higher RF power enhance the deposition rate and crystallinity. The emission from D-5(4) to F-7(J) (J = 6-0) of Tb3+ are observed on all the films. The intensity of PL spectra of crystalline films is obviously stronger than that of the amorphous films. The PL intensity of D-5(4) D-4 to F-7(6) is the strongest for crystalline film, but for amorphous film that of D-5(4) to F-7(5) is the strongest. Time-resolved spectra show that there exist two decay time for D-5(4) to F-7(j) (J = 6,5): one is shorter ranging from 41 to 60 mu s, the other is longer ranging from 202 to 287 mu s. The decay time of amorphous film is slightly longer than that of crystalline films. (c) 2004 Published by Elsevier B.V.

The Nd 1− x Y x Co 6.86 Hf 0.14 compounds with x =0–0.4 have been investigated by means of X-ray powder diffraction and magnetic measurements. The as-cast Nd 1− x Y x (Co,Hf) 7 compounds crystallize in the hexagonal TbCu 7 -type structure with the space group P6/mmm. The lattice parameter a and the cell volume V decrease linearly with the Y content while c holds almost constant. The saturation moment per formula unit decreases linearly with the Y content, but the saturation moment per Co atom increases with the Y content. The Curie temperature and the magnetic anisotropy field of the compounds increase with the Y content. The increase of the Curie temperature is mainly related to the increase of the Co–Co exchange interaction due to the volume reduction effect. The Nd 1− x Y x (Co,Hf) 7 compounds with x =0–0.4 show basal plane anisotropy at 5 K. The room temperature easy magnetization direction of the Nd 1− x Y x (Co,Hf) 7 compounds changes from basal plane to c -axis with increase in the Y content. The spin reorientation (SR) transition has been found in the Nd 1− x Y x (Co,Hf) 7 compounds and the SR temperature decreases with the Y content.

A serial of samples in Y2O3-Ga2O3-Tm2O3 pseudo-ternary system are prepared by solid-state chemical reaction method. The range of solid solution in (Y1-xTmx)(3)GaO6 is 0 F-3(4) transition at room temperatures with two lifetimes (similar to 5 and similar to 15 mu s) and a narrow saturation range of PL intensity for the Tm3+ content from x = 0.005 to 0.03. The sharp emission and long lifetime of (Y1-xTmx)(3)GaO6 indicate that Y3GaO6 is a potential phosphor and laser crystal host material. (c) 2005 Elsevier Inc. All rights reserved.

The structure, magnetization and magnetostriction of Laves phase compound TbCo2 are investigated by temperature dependent high resolution neutron powder diffraction. The compound crystallizes in the cubic Laves phase C15 structure above its Curie temperature T-c and exhibits a rhombohedral distortion (space group R (3) over barm) below T-c. By an appropriate extrapolation of the temperature factor of Co atom above Tc, the Rietveld refinement of the neutron powder diffraction data of the rhombohedral structure converges satisfactorily and reveals that the moments of Co1(3b) and Co2(9e) are almost equal. Tb moment follows well the Brillouin function. The total magnetic moment of TbCo2 is about 5-8mu(B)/f.u., the anisotropic magnetostriction constant lambda(111) is about 4.6 x 10(-3) and the volume magnetostriction omega(s) is about 8.7 x 10(-3) at 14 K. (C) 2004 Elsevier B.V. All rights reserved.

The compound FeSr(2)NdCu(2)O(7+delta) (Fe1212) was successfully synthesized by solid-state reaction. X-ray diffraction data indicate that the sample is of single phase. Rietveld whole-pattern-fitting method was used to refine the crystal structure of samples prepared under different annealing conditions using the tetragonal system with space group P4/mmm. Magnetization measurements indicate that magnetic susceptibility chi changes with temperature in a Curie-type manner. Resistance measurements indicate that these samples have a semiconductor-like behavior.

We have investigated the crystal structure, magnetization and magnetoresistance of the double perovskite compounds Sr-2(Fe1-xVx)MoO6(0less than or equal to xless than or equal to 0.1). The lattice constants and the cation ordering decrease monotonously with the V content. The Curie temperature, saturation magnetization and low field magnetoresistance of the compounds decrease with increasing x due to the reduced degree of ordering. The resistivity of Sr2FeMoO6 and lightly doped samples shows semiconductive behavior, while the samples with higher doping levels exhibit a semiconductor-metal transition around 80 K. (C) 2004 Elsevier Ltd. All rights reserved.

In contrast to the substitution of exotic elements such as Mn, Cu for Fe or W for Mo in Sr2FeMoO6, the degree of ordering of Fe and Mo in Sr2FexMo2−xO6 shows a maximum at xC=0.95 and decreases as x deviates from xC. Saturation magnetization depends upon composition in a similar way. It is shown that the entropy due to antisite defects or substitutional disorder can stabilize the double perovskite structure. It is proposed that the stability of the double perovskite structure of Sr2FexMo2−xO6 is essentially determined by the combined contribution to free energy of configuration entropy and differences in ionic charge and in ionic radius. A plausible charge distribution of Fe and Mo cations in Sr2FexMo2−xO6 is proposed to elucidate the observed composition-dependence of magnetization.

Ln(3+) (Ln = Nd, Sm, Eu, Gd, Dy, Ho, Er)-doped Y3GaO6 compounds were prepared by solid-state reaction, and their optical spectra such as absorption, photoluminescence, excitation and time-resolved spectra have been measured for Ln Nd, Sm, Dy, Ho, Er. X-ray powder diffraction shows that the lattice parameters of the compounds (Y(0.96)Ln(0.04))(3)GaO6 decrease with the decrease of the radii of trivalent Ln(3+) ions, indicating that Ln(3+) ions have substituted for y(3+) ions in the lattice. Optical spectra show that there are obvious absorptions at ultraviolet to visible region. The strong emissions in visible and infra-red region show that Y3GaO6 is a suitable host for rare-earth-doped laser crystal and phosphor materials. (C) 2004 Elsevier B.V. All rights reserved.

A new method, namely UACIEM, to extract reliable intensities of nonequivalent systematical overlapping reflections has been proposed and tested by simulated powder diffraction data from known crystal structures. Using both crystallographic and structural chemistry information, the method reconstructs diffraction intensities and solves a crystal structure through an iterative procedure. Our study shows that UACIEM is successful for cases where more than 30% of the total scattering power is located with precision from equivalent systematical overlapping reflections. The UACIEM process is not needed when equivalent systematical overlapping reflections are sufficient to reveal a crystal structure. UACIEM may fail in cases when: (i) only a small portion of the total scattering power (e.g., less than 7%) can be located, and (ii) most of the total scattering power (e.g., 95%) is located, but the atomic coordinates are not accurately known. The UACIEM method is superior to the simple equipartition methods for nonequivalent systematical overlapping reflections. (C) 2004 International Centre for Diffraction Data.

Pr1+xBa2−xCu3O7±δ solid solution was investigated by means of X-ray powder diffraction and Rietveld analysis. Single-phase PrBa2Cu3O7±δ (Pr123) can be synthesized under a Pr-rich condition by sintering at 950 °C in air. The solubility of Pr1+xBa2−xCu3O7±δ solid solution is 0.08≤x≤0.80. The structure of Pr1+xBa2−xCu3O7±δ is orthorhombic for 0.08≤xx≤0.80. To form single-phase Pr123, the Ba sites in the Pr123 structure are partially occupied by excess Pr ions, and the smallest amount of excess Pr is x=0.08. Meanwhile, all Ba ions stay in the Ba sites.

The crystal structure of new compound Ba3BPO7 was determined by ab initio method from high-resolution conventional X-ray powder diffraction data. The Rietveld refinement converged to R-p = 5.92%, R-wp = 8.87%, R-exp = 5.00% with the following details: Hexagonal, space group P6(3)mc, a = 5.4898 (1) Angstrom, c = 14.7551 (1) Angstrom, Z = 2. The basic unit of the structure is the [BaO10]-[BO3]-[PO4] polar polyhedra-chain composed of Ba1-B-P-O cluster. These chains, running along c-axis, stack in a HCP mode to build the whole structure wish triangular prism channels. The channels are parallel to c-axis too, in which Ba2 and Ba3 are located. (C) 2004 Elsevier Inc. All rights reserved.

The Nd1-xYxCo9.5V2.5 compounds with x = 0-1 crystallize in the tetragonal ThMn12 structure. The lattice parameters a, c and the cell volume V decrease with increasing Y content. The Curie temperature increases for x less than or equal to 0.2, then decreases with increase of the Y content. The exchange field coefficient n(RCo) was derived from the Curie temperature and follows the general trend of rare-earth-3d intermetallic interaction exchange. The high field saturation magnetization decreases with increase of the Y content. A domain wall pinning phenomenon was observed in all of the compounds and the substitution of Y for Nd makes this phenomenon less obvious. High field measurements of the magnetization show a field induced metamagnetic transition in each compound and the critical field H-crit(H) decreases with increase of the Y content.

Nd1-xSrxCoO3 polycrystals have been prepared in the compositional range 0 0) is observed for x > 0.4. All other compounds show activated behaviour: drho/dT < 0. A higher order transition is observed in the heat conductivity kappa(T) and the thermopower S(T) of the base compound around T-s = 200 K which gradually smoothens out with increasing Sr-content. Specifically, we propose a low spin-low spin approach transition which involves phonons in a way similar to the dynamic Jahn-Teller effect. (C) 2003 Elsevier B.V. All rights reserved.

The crystal structures of a series of compounds with the composition Ln(3)GaO(6)(Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er) synthesized by solid-state reaction at 1400degreesC are investigated. X-ray diffraction shows that Ln3GaO6 has a non-centro symmetric orthorhombic structure (space group Cmc2(1)). Lattice parameters a, b, c and cell volume and the average distances between Ln(l)-O, Ln(2)-O of these compounds decrease with the decreasing of the radii of trivalent Ln ions, which accord with the expected lanthanide contraction behavior. There are two sites of seven-fold coordination for Ln atoms with oxygens, and Ga atoms are in oxygen tetrahedra which are distorted and elongated along the a-axis. Magnetization measurements indicate that the susceptibility X changes with temperature in Curie-type manner. (C) 2004 Elsevier Inc. All rights reserved.

The crystal structure and magnetostriction of Nd1-xTbxCo2 compounds were investigated by temperature dependent X-ray powder diffraction. It is revealed that all samples retain the cubic Laves phase C15 structure above their Curie temperature T-C. A rhombohedral distortion at low temperature is revealed for the samples from x = 0.4 to 1.0 and the temperature dependence of the anisotropic magnetostriction constant lambda(111) is calculated. The anisotropy constant K-1 exhibits a minimum value between x = 0.3 and 0.4. The calculated spontaneous volume magnetostriction exhibits an anomaly between x = 0.3 and 0.4, which is likely to be associated with an abrupt change of the Co moment in this concentration region. (C) 2003 Elsevier B.V. All rights reserved.

We have investigated the structure and magnetic properties of Pr 1− δ (Co,Cu) 5+2 δ (0 δ 7 -type structure, using X-ray powder diffraction and magnetic measurements. The lattice parameters ( a and c ) of Pr 1− δ (Co,Cu) 5+2 δ compounds increase with increasing Cu content since the radius of Cu is a little larger than that of Co. Our experimental results indicate that Cu may stabilize Pr 1− δ (Co,Cu) 5+2 δ compounds with the TbCu 7 -type structure, but δ is only determined by the temperature. The X-ray patterns of magnetically aligned samples show that the compounds with x =2.0 and 3.0 exhibit easy-plane magnetocrystalline anisotropy. The saturation magnetization and Curie temperature decrease with increasing Cu content.

The crystal structure and magnetization of Hf0.8Ta0.2(Fe1-xCOx)(2) are investigated by X-ray powder diffraction and magnetization measurements. The compounds exhibit the Laves C14 structure for x = 0.0-0.2 and the C15 structure for x greater than or equal to 0.3. The structural transition from C14 to C15 leads to an anomaly of the unit cell volume between x = 0.2 and 0.3. When x = 0.0, the compound undergoes a magnetic phase transition from ferromagnetic to paramagnetic state via the antiferromagnetic state, in which a field-induced metamagnetic transition is observed. When x = 0.1 and 0.2, the compounds exhibit unusually small saturation moments, which are considered as antiferromagnetism (with weak ferromagnetic impurities) and weak ferromagnetism or ferrimagnetism, respectively. The formation of the AFM state is associated with a small bond length of Fe atom in the 6h site. When x greater than or equal to 0.3, the compounds exhibit a ferromagnetic to paramagnetic transition, which can be explained by itinerant electron metamagnetism. (C) 2003 Elsevier B.V. All rights reserved.

The PrBa(2-x)Sr(x)Cu(3)O(7+/-delta) solid solution was investigated by means of X-ray powder diffraction in combination with Rietveld analysis. The Sr-doped Pr123 single phase could be synthesized at 950degreesC in air. The solubility of PrBa(2-x)Sr(x)Cu(3)O(7+/-delta) solid solution is 0.2 less than or equal to x less than or equal to 0.6. The structure of PrBa(2-x)Sr(x)Cu(3)O(7+/-delta) is orthorhombic for x = 0.2. The structure transforms into tetragonal for 0.3 less than or equal to x less than or equal to 0.6. In the PrBa(2-x)Sr(x)Cu(3)O(7+/-delta) structure, Sr ions can replace Ba ions, the highest value is x = 0.6 under our experimental condition. But Sr ions could not replace Pr ions. Furthermore Pr ions could not occupy the sites of Ba ions in the PrBa(2-x)Sr(x)Cu(3)O(7+/-delta) system. Both ionic radii and chemical properties play an important role in the mutual substitution of Pr, Ba and Sr ions in the Pr123 structure of the PrBa(2-x)Sr(x)Cu(3)O(7+/-delta) system. (C) 2003 Elsevier B.V. All rights reserved.

The coexistence of superconductivity and magnetic order seems to take place in the so-called ruthenate-cuprates (Ru-1212). A systematic study is carried out on crystal structure of the RuSr 2 R Cu 2 O 8− δ phases ( R =Gd, Tb, Dy, Y, Ho, Er) synthesized under high pressure by X-ray powder diffraction. RuSr 2 R Cu 2 O 8− δ ( R =Gd, Tb, Dy, Y, Ho, Er) has the Ru-1212-type structure of a tetragonal symmetry and the RuO 6 octahedra rotate around the c -axis with an additional small rotation around an axis perpendicular to c . The DC-magnetization data establish that compounds with R =Gd, Y, Ho, Er exhibit ferromagnetic order below about 140 K, and the Meissner effect was observed at low temperature for R =Y compound.

The crystal structure, electronic transport and magnetic properties of double perovskite (Sr2−xBax)FeMoO6 () are investigated. These compounds exhibit a metal–insulator transition as a function of doping x. The valence transition from Fe3+–Mo5+ to Fe2+–Mo6+ when x exceeds the critical concentration x = 1.6 can lead to a localization of the itinerant electrons and plays a key role in the metal–insulator transition. The bond distance data and composition dependence of the Curie temperature and magnetoresistance suggest this valence transition. The Curie temperature TC shows an enhancement on the Ba-poor side and decreases monotonically with x on the Ba-rich side, which can be understood in terms of two competing effects: anti-site defects and chemical pressure. The low field magnetoresistance shows a close correlation with the Curie temperature of the compounds.

X-ray powder diffraction and magnetization measurements reveal that light rare earth and heavy rare earth have different effects on the structure, Curie temperature and magnetic phase transition of the compounds R(Co1-xGax)(2) (R = Nd, Gd, Tb, Dy) (x = 0.0-0.3). The lattice constant exhibits a giant increase with increasing Ga concentration in all compounds. The Curie temperature shows no variation for R = Nd, a monotonic decrease for R = Gd and a maximum for R=Tb and Dy, respectively. The Curie temperature is strongly related with volume expansion, in which a critical value of a(c) approximate to 7.26 Angstrom is reached. The observed magnetic transition in all compounds is well explained within the framework of the Inoue-Shimizu model. It is revealed that both the lattice constant and the Curie temperature have a strong relationship with the order of the magnetic phase transition. (C) 2003 Elsevier B.V. All rights reserved.

The crystal structure and magnetic properties of Sr-2(Fe1-xCrx)MoO6 (0 less than or equal to x less than or equal to 0.4) have been investigated. In contrast to Sr-2(Fe1-xMnx)MoO6 and Sr2Fe(Mo1-xWx)O-6, the Cr doping results in a decrease of cationic ordering in Sr-2(Fe1-xCrx)MoO6. The saturation magnetization decreases with x and exhibits a linear dependence on the anti-site defect concentration. All the samples exhibit a semiconductor-metal transition. The low-field magnetoresistance increases with the saturation magnetization in a non-linear way. By assuming a preferential occupation of the Cr ions at the Mo sites, the dependence of magnetization on the Cr content can be well explained within a simple ferrimagnetic model. (C) 2003 Elsevier B.V. All rights reserved.

The Pr1+xBa2-xCu3O7±δ solid solution was investigated by means of X-ray powder diffraction combined with Rietveld analysis. A Pr123 single phase could be synthesized under Pr-rich conditions by sintering at 950 °C in air. The solubility range of Pr1+xBa2-xCu3O7±δ solid solution is 0.08≤x≤0.80. The structure of Pr1+xBa2-xCu3O7±δ for 0.08≤x

Subsolidus phase relations of the constant copper oxide content (50 mol%) section in the PrO(11/6)-BaO-CaO-CuO system at 950 degreesC in air are investigated by means of X-ray diffraction analyses. The phase relations consist of I single-phase region, I two-phase region, 2 three-phase regions and 6 four-phase regions. Mutual substitutions among Pr, Ba and Ca in the Pr123 structure were studied in detail. The result indicates that Ba ions can be replaced exclusively by Pr ions, but not by Ca ions, whereas Ca ions can partially occupy the sites of Pr ions. The ionic radius plays a more important role than the chemical property for substitution among Pr, Ba and Ca ions in the Pr123 structure. (C) 2003 Elsevier B.V. All fights reserved.

The mixing effects of light and heavy rare earths in cubic Laves phase compounds Nd1-xHRxCO2 (HR = Gd, Tb) have been investigated by means of x-ray powder diffraction and magnetic measurements. In Nd1-xTbxCo2, the saturation moment M-S exhibits in anomaly and could be ascribed to an abrupt jump of the Co moment at a critical concentration x approximate to 0.33, whereas, in Nd1-xGdxCo2, M-S does not show such an anomaly and a relatively simple magnetic behaviour is observed at x(c) approximate to 0.43. The different behaviours of these two systems can be understood by considering the structural distortion of a cubic unit cell at low temperature. A field-induced metamagnetic transition from weak ferrimagnetism to strong ferrimagnetism is observed in both systems. This can be interpreted by the evolution of magnetization with the help of percolation theory. The compensation points are observed in both systems, which are well explained within the two-sublattice model. A double peak of the AC susceptibility observed in Nd1-xTbxCo2 near x(0) approximate to 0.19 does not necessarily mean the occurrence of a first-order phase transition. The observed second-order magnetic phase transition near x(0) can be well described by Landau theory of the phase transition.

We have investigated the structural stability and magnetic properties of SMCo7-xCu, compounds with the TbCu7-type structure using x-ray powder diffraction and magnetic measurement. A large solid solution with 0.8 less than or equal to x less than or equal to 4.0 in SMCo7-xCux compounds has been observed. Both the lattice parameters and unit cell volume increase with increasing Cu content. SMCo7-xCux compounds exhibit ferromagnetic order. A strong uniaxial magnetocrystalline anisotropy with an anisotropy field as high as 20 T is obtained with x = 0.8 at 5 K. However, the saturation magnetization and Curie temperature decrease with increasing Cu content.

The electronic transport properties of the ordered double perovskite oxides Sr2FexMo2-xO6 (0.8 less than or equal to x less than or equal to 1.5) have been investigated. In this system, the samples (x greater than or equal to 1.2) are semiconducting in the temperature range of 4.2 less than or equal to T less than or equal to 300 K. A metal-semiconductor transition occurs when x < 1.2 and the transition temperature T-MS decreases obviously as the Fe, content decreases. Rietveld refinement of the X-ray powder. diffraction profiles indicates that the crystal structure of the compounds Sr2FexMo2-xO6 changes from a tetragonal I4/mmm lattice to a cubic Fm (3) over barm lattice around x = 1.2. (C) 2003 Elsevier Science B.V. All rights reserved.

The subsolidus phase relations of R2O3-CaO-CuO ternary systems (R = Nd, Sm, Gd, Tm) have been investigated by X-ray powder diffraction. All samples were synthesized at about 950degrees in air. There exists a ternary compound Ca14-xRxCu24O41 (x = 4 for R = Nd, Gd and x = 5 for R = Sm) and a ternary solid solution Ca2+xR2-xCu5O10 (R = Nd, Sm, Gd, Tm) with a wide composition range Deltax of about 0.6. The compound Ca14-xRxCu24O41 possesses a layered orthorhombic structure and is isostructural to Sr14-xCaxCu24O41. The lattice parameters a and c of the compound are basically independent of the ionic radius of R, while the lattice parameter b and unit-cell volume V decrease substantially with the decrease of the ionic radii of R. The Ca2+xR2-xCu5O10 solid solution is isostructural to Ca2+xY2-xCu5O10, the structure of which is based on an orthorhombic "NaCuO2-type" subcell containing infinite one-dimensional chains of edge-shared square planar cuprate groups crosslinked by the layered cations Ca and R that locate in the inter-chain tunnels. (C) 2002 Elsevier Science (USA). All rights reserved.

The structural stability of La2Co17- xMx ( M = Mn, Mo, Nb, Ti, V, Al, Cr, Ni and Si) based on the interatomic potential has been studied. The calculated site preference of the third element M is found to be the 6c site, which is in agreement with the experiments. In the calculations, if the crystal cohesive energy of La2Co16Mn is taken as the highest one in the crystallization of La2Co17- xMx, the lowest content x of the third element M ( M = Mn, Mo, Nb, Ti and V) required to stabilize La2Co17- xMx, is near that found in the experiments. The differences of the cell parameters between the calculated and the experimental values are less than 0.4%. The differences of the atomic parameters for Co ( or M) between the calculated and the experimental values are about or even smaller than 1%, and that of La is about 3%. Because the energies of La( Co1-xAlx)(13) are lower than those of La-2(Co1-xAlx)(17), La-2(Co1- xAlx)(17) could not be formed in the experiments. In the calculations, with either a range of deformation of the structure or the reconstruction of the initial structure La2Co17 from LaCo5, the same results including the cohesive energy curves and the crystallographic parameters can be retrieved after the action of the interatomic potentials.

Serial single-phase Gd-2(Fe1-x-yCoyTix)(17) compounds have been synthesized. These compounds have a crystal structure belonging to rhombohedral lattice with R (3) over barm space group. The lattice parameters of compounds decrease with cobalt content and increase with titanium content, respectively. The saturation magnetization decreases with increasing cobalt and titanium contents. The anisotropy fields increase to maximum then decrease with cobalt concentration. The magnetocrystalline anisotropy constants increase with cobalt content from negative to positive maximum and then decrease with Co concentration. The saturation moment of the compounds decreases linearly with cobalt concentration and decreases nonlinearly with titanium concentration. (C) 2002 Elsevier Science B.V. All rights reserved.

The crystal structure and magnetic properties of a new series of ordered double-perovskite oxides Sr2FexMo2-xO6 (0.8 less than or equal to x less than or equal to 1.5) have been studied. The crystal structure changes from a tetragonal I4/mmm lattice to a cubic Fm (3) over barm lattice around x = 1.2. The degree of ordering in Sr2FexMo2-xO6 exhibits a maximal at x = 0.95 and decreases as x deviates from 0.95. The saturated magnetization increases from x = 0.8 to 0.95 and then decreases from x = 0.95 to 1.5. The Curie temperature exhibits an abrupt drop around x = 1.2, where the structural transition takes place. These complex behaviours are strongly correlated to antisite defect concentration in the compounds.

A novel surface modified complex strontium titanate used as dispersion particles in an electrorhelogical fluid with an extraordinary high yield stress was synthesized by means of a modified sol-gel technique and characterized by X-ray powder diffraction. The structure model free full profile fitting technique was used to derive the crystallographic data of the compound, which crystallized in a monoclinic lattice with a = 13.6822(7), b = 14.5549(6), c = 12.7423(5) Angstrom and beta = 91.803(2)degrees. Deliberate examination of the XRD pattern indicates that the most probable space group of the compound is P2(1)/n. A possible composition of the complex strontium titanate is Sr[TiO4(C2O4)(2)].3H(2)O with eight chemical formula units per unit cell, leading to a calculated density of D-x=2.25 a/cm(3) in good agreement with the measured density of D-m= 2.28(5) g/cm(3). (C) 2002 Elsevier Science B.V. All rights reserved.

The temperature dependences of the resistivity ρ and the heat conductivity κ of La 0.7 Ca 0.3 Mn 1− x Fe x O 3− δ (0 x κ is dominated by the lattice contribution and changes from a crystalline to a randomized scenario with increasing Fe-content. We also observe a splitting of the Curie and metal–insulator transition temperature T c > T mi which we assign mainly to a small oxygen deficit in the TTE-measured sample surface layer. Steps in κ at T mi , Δ κ mi , are assigned to polaronic effects. Δ κ mi changes sign with increasing x , suggesting that Fe–Fe pairs in octahedral settings take over from the single Fe-sites (dilute limit) already at x =0.04. For x >0.06, structures in κ ( T ) suggest that larger Fe-based clusters are introduced.

High-temperature (1273 K) phase relationships in the pseudobinary system RE5Si4-RE5Ge4 (RE=Nd and Pr) were studied by X-ray powder diffraction (XRD). Three structurally distinct phase regions exist in the Nd5Si4-xGex system: the Nd5Si4-based solid solution crystallizing in the tetragonal Zr5Si4-type Structure with space group P4(1)2(1)2, the Nd5Ge4-based solid solution crystallizing in the orthorhombic Gd5Ge4-type structure with space group Pnma and a ternary intermediate phase crystallizing in the monoclinic Gd5Si2Ge2-type structure with space group P112(1)/a. In the Pr5Si4-xGex system, there are only two structurally distinct phase regions: the Pr5Si4-based solid solution crystallizing in the tetragonal Zr5Si4-type structure with space group P4(1)2(1)2 and the Pr5Ge4-based solid solution crystallizing in the orthorhombic Gd5Ge4-type structure with space group Pnma. The Rietveld powder diffraction profile fitting technique was used for the refinement of crystal structures. The lattice parameters, atomic positions and interatomic distances in the high-temperature Nd5Si2.8Ge1.2, Nd5Si2Ge2 and Pr5Si2Ge2 compounds were derived. (C) 2002 Elsevier Science B.V. All rights reserved.

The temperature dependences of the magnetoresistance Δρ/ρ and the thermoelectric power S of La0.7Ca0.3Mn1−xFexO3−δ (0 Tmi.

The crystal structure and magnetic properties of Gd-5(Si1-xGex)(4) compounds (0 less than or equal to x less than or equal to 1.0) are investigated by means of temperature dependent X-ray powder diffraction and magnetic measurements. A crystallographic and magnetic phase diagram of the pseudobinary system Gd5Si4-Gd5Ge4 is constructed. An intriguing observation is that Gd-5(Si1-xGex)(4) alloys form a completely miscible solid-solution at low temperature (< T-C), crystallizing in the Gd5Si4-type structure as indicated by the well-defined linear dependence of lattice parameters on germanium concentration x, and decomposing into three partially miscible solid-solutions above the Curie temperature, i.e. Gd5Si4 based (x < 0.5), Gd5Ge4 based (x greater than or equal to 0.8) and Gd5Si2Ge2 based (0.5 less than or equal to x < 0.8) solid-solutions, This unusual feature can be understood by taking into account competing effects of ferromagnetic exchange interaction and lattice strain in the solid-solution. (C) 2001 Elsevier Science B.V. All rights reserved.

The structure and magnetic properties of a ternary intermetallic compound Gd3Fe28Re stabilized by Re in the sixth period has been investigated by means of XRD analysis and magnetic measurement. The compound crystallizes in the monoclinic Nd3(Fe,Ti)29-type structure with space group A2/m. The lattice parameters are a = 10.5778(1) A, b = 8.5317(1) A, c = 9.6945(2) A, and β = 96.85(1)°. The preferential occupancy of Re over the 4g, 4i3 and 4i4 crystallographic sites were determined successfully by Rietveld refinement of XRD data, which is basically attributed to the effect of size. The compound exhibits planar magnetocrystalline anisotropy perpendicular to the [204] direction. The Curie temperature TC, the saturation moment MS and the magnetocrystalline anisotropy field HA are derived to be 467 K, 35.1 µB f.u.-1 and 69.4 kOe, respectively.

The effect of substitution of Ni for Co in the borides Nd/sub 3/(Co/sub 13-x/Ni/sub x/)B/sub 2/ (x=0, 1, 2, 3, 4, 5) on the crystal structure and magnetic properties has been investigated. The lattice parameter a decreases while c increases with increasing x in the range 0/spl les/x/spl les/5. The Curie temperature and saturation magnetic moment per formula unit in Nd/sub 3/(Co/sub 13-x/Ni/sub x/)B/sub 2/ decrease monotonically as the Ni concentration increases. We have observed spin-reorientation transitions at temperatures that decrease monotonically with increasing Ni concentration. It is noteworthy that the substitution of Ni has a significant effect on the magnetocrystalline anisotropy of the Co sublattice, leading to the change of easy magnetization direction of Nd/sub 3/(Co/sub 13-x/Ni/sub x/)B/sub 2/ compounds from basal plane to the c axis at room temperature when x/spl ges/2. The magnetic phase diagram of the Nd/sub 3/(Co/sub 13-x/Ni/sub x/)B/sub 2/ borides is given, and the behavior of magnetocrystalline anisotropy is analyzed by the single ion model.

A series of Gd-3(Fe1-x-yCoyTix)(29) (x = 0.011-0.034, y = 0-0.393) Samples have been prepared. Single-phase samples assigned as 3:29 compounds with the monoclinic lattice are obtained in the following composition regions: x; = 0.011, 0 less than or equal to y less than or equal to 0.307; x = 0.022, 0 less than or equal to y less than or equal to 0.313; and x = 0.034, 0 less than or equal to y less than or equal to 0.393. The solid-solution limit of cobalt in Gd-3(Fe1-x-yCOyTix)(29) increases with the Ti content. The cell parameters a, b and c show anisotropic decreases with the Co content, i.e. a and b decrease significantly and c decreases slightly in the composition range investigated. The Curie temperature is increased by the substitution of Co for Fe in Gd-3(Fe1-x-yCoyTx)(29). The saturation magnetization first increases and then decreases with the Co content. The dependence of the intrinsic magnetic properties of Gd-3(Fe1-x-yCoyTix)(29) on the Co and Ti contents is presented. The compounds exhibit an easy-magnetization direction on the a-b plane corresponding to the CaCu5-type structure at room temperature. The anisotropy field H-a of Gd-3(Fe1-x-yCoyTix)(29) is decreased and the magnetocrystalline anisotropy constant K-1 is increased by the substitution of Co for Fe. No spin reorientation is observed in the alternating-current susceptibility measurement between 77 K and the Curie temperature.