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Abstract: The structural and magnetic properties of the Nd2Co7−x Fe x compounds related to R m+n T2m+5n series (R=rare earth, T=transition metal) were investigated by means of X-ray diffraction and magnetic measurements. The compounds crystallize in the Ce2Ni7-type structure with the space group P63/mmc between x =0.0 and 2.1. For higher Fe content the Nd2(CoFe)7 either coexists with the Nd(CoFe)3 phase (x >2.1) or decomposes to Nd(CoFe)3 +Nd2(CoFe)17 (x >2.4). The single phase Nd2Co7−x Fe x compounds exhibit two spin-reorientation transitions (SRT) for x <1.5. The substitution of Fe for Co elevates both the spin-reorientation transition temperatures for x <1.5 and finally leads to a single ferromagnetism to paramagnetism transition for x ≥1.5. A magnetic phase diagram is constructed based on the magnetic measurements, thermogravimetry analysis under a low magnetic field and X-ray diffraction of magnetically aligned samples. The saturation magnetization of the compounds increases gradually first with the Fe content for x ≤0.20, substantially for 0.20< x <1.5, and then decreases for x >1.5, which can be elucidated by a depletion effect of d band electrons due to the substitution of Fe for Co and the spin-flipping due to an enhanced d band splitting. [Copyright &y& Elsevier]

Abstract: The crystal structure and physical properties of Bi1− x Gd x FeO3 ceramics with x ≤0.5 have been studied by X-ray diffraction, differential scanning calorimetry, dielectric and magnetic measurements. Bi1− x Gd x FeO3 compounds crystallize at room temperature in R3c structure for x <0.08 and in Pbnm structure for x ≥0.3. The R3c phase transforms to the Pbnm phase as temperature increases. Temperature-dependent dielectric response and low-temperature X-ray diffraction indicate a phase transition of the Pbnm phase at low-temperature. Detailed structural analysis indicates that the interaction between Bi and O plays an important role in the evolution of structure and physical properties. A phase diagram is constructed to illustrate the physical property–composition–temperature relations. [Copyright &y& Elsevier]

Hole-doped double perovskite compounds (Sr,Na)2FeMoO6 with the Na content of x=0,0.02,0.03,0.07 and 0.17 have been synthesized by sol–gel method. Effects of hole doping on the crystal structure and magnetic properties of Sr2FeMoO6 have been investigated by means of X-ray powder diffraction (XRD) and magnetic measurements. The XRD pattern indicates that all the samples are of single phase and belong to the space group I4/m. Due to the smaller ionic radius of Na+ than that of Sr2+ ions, the lattice constants and unit cell volume of the compound decrease slightly with x. The degree of cation ordering in the Na-doped Sr2FeMoO6 compounds shows a non-monotonic variation with the doping level, increasing from x=0 to x=0.03 and decreasing slightly with further increase of the doping. In contrast to the composition dependence of the degree of ordering, the Curie temperature of the compound decreases at low doping level and increases at high doping level. The saturation magnetization of the compound increases with x for x<0.17. Similar to the electron-doped Sr2FeMoO6, provided that the doped hole enters selectively the spin-down band, the variation of the saturation magnetization can be explained in light of the ferrimagnetic model (FIM). [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure and magnetic properties of mixed rare earth Nd2−x Er x Fe17 compounds (0≤ x ≤2.0) were investigated by means of X-ray powder diffraction (XRD) and magnetic measurements. The compounds crystallize in the rhombohedral Th2Zn17-type structure for x ≤0.5 and in the hexagonal Th2Ni17-type structure for x =2.0. Coexistence of the Th2Zn17- and the Th2Ni17-type structures is observed for x =1.0 and 1.5. Violating the Gibbs’ phase rule for a binary system, the linear decrease of the unit-cell volume with the Er concentration persists even in the two-phase region, implying an allotropic character of the coexisting Th2Zn17 and Th2Ni17 phases in the samples with x =1.0 and 1.5. Thermomagnetic measurements show only one magnetic ordering temperature for the samples in the two-phase region, but temperature dependent XRD reveal obvious magnetovolume effects in both the phases around the magnetic ordering temperature. The saturation magnetization of the compounds exhibits a linear dependence on the Er concentration, indicating an ideal mixing effect of the rare earths on the magnetization in spite of the different crystal structures of the parent compounds. [Copyright &y& Elsevier]

Abstract: Crystal structure, magnetic and electrical-transport properties of the rare-earth-doped compounds (Sr1.85Ln0.15)FeMoO6 (Ln=Sr, La, Ce, Pr, Nd, Sm and Eu) have been investigated by means of X-ray diffraction, magnetic and electric measurements. All the samples are single phase and belong to the I4/m space group. Due to the competing contributions of electron doping and steric effects, the unit-cell volume of the doped compounds changes slightly and does not vary systematically with the ionic radius of the rare-earth ions. The temperature dependence of the magnetization of (Sr1.85Ln0.15)FeMoO6 indicates that the Curie temperature of the doped compounds has increased upon doping, except for the Eu-doped compound. The saturation magnetization of the compounds at 5K cannot be explained simply by considering the ferrimagnetic arrangement of the magnetic sublattices of Fe and Mo because of the magnetic contribution of rare-earth ions. However, the saturation magnetization at 100K of the doped compounds exhibits a linear decrease with the increase of the anti-site defect concentration. Comparison of the saturation magnetization of the compounds at 5 and 100K suggests that at 5K the magnetic moments of Ce, Pr, Nd and Sm align parallel with that of Fe, while the magnetic moment of Eu is anti-parallel with that of Fe. The normalized resistivities of the parent and the La- and Sm-doped compounds exhibit a semiconductor-metal transition, while the Pr-, Nd- and Eu-doped compounds exhibit semiconducting behavior. [Copyright &y& Elsevier]

Abstract: The crystal structure and magnetic properties of Nd2−x Tb x Fe17 and NdTbFe17−y Al y compounds were studied by means of X-ray diffraction and magnetization measurements. All the samples show the rhombohedral Th2Zn17-type structure with space group . For Nd2−x Tb x Fe17 compounds, the lattice parameters decrease with increasing Tb concentration, and the Curie temperature increases with the Tb content while the saturation magnetization decreases linearly at a rate of 10.54μ B/f.u. per Tb atom. For NdTbFe17−y Al y compounds, the substitution of Al for Fe leads to an increase in lattice parameters a, c and unit-cell volume V. The Al atoms preferentially occupy 18h site at low Al concentration whereas prefer to occupy 6c and 18f sites at high Al concentration. The Curie temperature increases with Al content up to y =3 then decreases for 3≤ y ≤8. X-ray diffraction of magnetically pre-aligned samples indicates that the easy magnetization direction of the samples changes from planar to c-axial with increasing aluminum concentration. The saturation magnetization of compounds decreases with increasing Al concentration. [Copyright &y& Elsevier]

Abstract: The crystal structure and magnetic properties of a series of ordered double perovskite oxides (Sr2−3 x La2 x Ba x )FeMoO6 () 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 lattice around . Though the nominal average size of the A site cation of (Sr2−3 x La2 x Ba x )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 (T M−S) is observed. The resistivity and T M−S of the compounds decrease with x for and increase for . 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. [Copyright &y& Elsevier]

Abstract: TbFe12− x Mo x 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 5K 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 due to hybridization of the Fe and Mo d-bands. [Copyright &y& Elsevier]

Abstract: 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 Sr2Fe x Mo2−x O6 shows a maximum at x C=0.95 and decreases as x deviates from x C. 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 Sr2Fe x Mo2−x O6 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 Sr2Fe x Mo2−x O6 is proposed to elucidate the observed composition-dependence of magnetization. [Copyright &y& Elsevier]

Abstract: The crystal structure and magnetic properties of (Nd x R1− x )3Fe24Cr5 (R=Gd and Tb) compounds with have been investigated by means of X-ray diffraction and magnetic measurements. All the samples are single phase and crystallize in the Nd3(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 (Nd x Gd1− x )3Fe24Cr5 and the (Nd x Tb1− x )3Fe24Cr5 compounds due to the lanthanide contraction. The room-temperature easy magnetization direction changes to the [040] direction with increasing Nd content. The Curie temperature of (Nd x Gd1− x )3Fe24Cr5 decreases monotonically upon substitution of Nd for Gd, while the Curie temperature of the (Nd x Tb1− x )3Fe24Cr5 compounds decreases with the Nd content for and increases for . 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. [Copyright &y& Elsevier]

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 TC. 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 λ111 is calculated. The anisotropy constant K1 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. [Copyright &y& Elsevier]

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≥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≥0.3, the compounds exhibit a ferromagnetic to paramagnetic transition, which can be explained by itinerant electron metamagnetism. [Copyright &y& Elsevier]

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 ac&ap;7.26 A˚ 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. [Copyright &y& Elsevier]

The crystal structure and magnetic properties of Sr2(Fe1−xCrx)MoO6 (0&les;x&les;0.4) have been investigated. In contrast to Sr2(Fe1−xMnx)MoO6 and Sr2Fe(Mo1−xWx)O6, the Cr doping results in a decrease of cationic ordering in Sr2(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. [Copyright &y& Elsevier]

Crystal structures of compounds at ambient temperature in the pseudobinary system Gd5Ge4–La5Ge4 were studied by X-ray powder diffraction (XRD). There exist three single-phase regions in this system. The crystal structure of Gd5Ge4, La5Ge4 and Gd3La2Ge4, which are prototype compounds in three phase regions, respectively, were reported. The Gd5Ge4 and La5Ge4 crystallize in the orthorhombic Sm5Ge4-type structure with space group Pnma. The ternary intermediate compound Gd3La2Ge4, which is determined for the first time, crystallizes in the monoclinic Gd5Si2Ge2-type structure with space group P1121/a. The Rietveld powder diffraction profile fitting technique was used for the refinement of crystal structure. The lattice parameters, atomic occupations, interatomic distances of the Gd5Ge4, La5Ge4 and Gd3La2Ge4 compounds were derived. [Copyright &y& Elsevier]

The structure and magnetic properties of the SmCo9.8V2.2 compound were investigated by means of X-ray diffraction analysis and magnetic measurement. SmCo9.8V2.2 crystallizes in a tetragonal structure with space group I4/mmm. The lattice parameters are a=8.3802(1) A˚ and c=4.7047(1) A˚. Both the atomic size effect and enthalpy effect favor a preferential occupation of V on the 8i site. Magnetic measurements indicate that the SmCo9.8V2.2 compound is ferromagnetic with a Curie temperature of 360 K. The easy magnetization direction of SmCo9.8V2.2 is perpendicular to the c-axis. The saturation magnetization and the magnetocrystalline anisotropy field of the SmCo9.8V2.2 compound at 5 K are 35.4 emu/g and 77 kOe, respectively. [Copyright &y& Elsevier]

The electronic transport properties of the ordered double perovskite oxides Sr2FexMo2−xO6 (0.8&les;x&les;1.5) have been investigated. In this system, the samples (x&ges;1.2) are semiconducting in the temperature range of 4.2&les;T&les;300 K. A metal–semiconductor transition occurs when x<1.2 and the transition temperature TMS 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 Fm3¯m lattice around x=1.2. [Copyright &y& Elsevier]

Magnetization and AC susceptibility measurements have been carried out to investigate the magnetic phase transition of Gd1−xDyxCo2 compounds. It is revealed that the type of the magnetic phase transition changes from second order to first order around xc=0.8 with the increase of Dy concentration. A satisfactory explanation is offered in terms of the Inoue-Shimizu model. The exchange-enhanced susceptibility of the compounds within the exchange-enhanced paramagnetism model is in good agreement with the 3d-electrons susceptibility deduced by Inoue–Shimizu model. [Copyright &y& Elsevier]

Serial single-phase Gd2(Fe1−x−yCoyTix)17 compounds have been synthesized. These compounds have a crystal structure belonging to rhombohedral lattice with R3¯m 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. [Copyright &y& Elsevier]

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 P41212, 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 P1121/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 P41212 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. [Copyright &y& Elsevier]

The crystal structure and magnetic properties of ternary compounds Nd5Si4−xGex (x=1.2 and 2) were investigated by means of X-ray powder diffraction and magnetic measurements. The as-cast samples α-Nd5Si2.8Ge1.2 and α-Nd5Si2Ge2 crystallize in the orthorhombic Gd5Si4-type structure with space group Pnma and the monoclinic Gd5Si2Ge2-type structure with space group P1121/a, respectively. The samples β-Nd5Si2.8Ge1.2 and β-Nd5Si2Ge2 annealed at 1273 K all crystallize in the tetragonal Zr5Si4-type structure with space group P41212. All phases of α-Nd5Si2.8Ge1.2, β-Nd5Si2.8Ge1.2, α-Nd5Si2Ge2 and β-Nd5Si2Ge2 exhibit a spin glasslike behavior and may have a canted magnetic structure. The Curie temperature shows a strong dependence on the crystal structure of the compounds. The average interatomic distances of magnetic Nd atoms and the amount of the covalent (Si,Ge)–(Si,Ge) bond pairs in these phases are different, which may be responsible for their different magnetic properties. [Copyright &y& Elsevier]

Phase relationships at ambient temperature in the pseudobinary system Nd5Si4–Nd5Ge4 were studied by X-ray powder diffraction (XRD). Four structurally distinct phase regions exist in this system. The Nd5Si4-based solid solution in which Ge statistically substitutes for Si crystallizes in the tetragonal Zr5Si4-type structure with space group P41212. The Nd5Ge4-based solid solution in which Si statistically substitutes for Ge crystallizes in the orthorhombic Gd5Ge4-type structure with space group Pnma. There are two ternary intermediate phases, which crystallize in the orthorhombic Gd5Si4-type structure with space group Pnma and the monoclinic Gd5Si2Ge2-type structure with space group P1121/a. The Rietveld powder diffraction profile fitting technique was used for refinement of the crystal structure. The lattice parameters, atomic positions and interatomic distances for Nd5Si4, Nd5Si2.8Ge1.2, Nd5Si2Ge2 and Nd5Ge4 were derived. [Copyright &y& Elsevier]