The crystal structures and physical properties of the solid solution compound Ba5Y8-xMn4021-1.5x （x = 0, 1）

New oxometallides with the formula Ba5Y8-xMn4021-1.5x （x = 0, 1） are prepared through an atmosphere-controlled solid-state reaction. Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4 （Y8） and 5/7/4 （Y7） are obtained. The crystal structures and the physical properties of the compounds are investigated by X-ray powder diffraction, magnetization, conductivity, and dielectricity measurements. The Ba5Y8-xMn4021-1.5x compound is demonstrated to be a Y-deficient solid solution. The solid solution compound Ba5Y8-xMn4021-1.5x crystallizes into tetragonal symmetry with the space group I4/m. Detailed structure analysis by Rietveld refinement of the X-ray powder diffraction data reveals that the Y vacancies occur preferentially at the Y（2） site. Thermal magnetization measurements indicate the presence of antiferromagnetic interaction between Mn ions in the compounds, and temperature-dependent resistivity measurements show that insulator-semiconductor transitions occur around 175 K and 170 K for the Y8 and Y7 samples, respectively. Strong frequency dependences of the dielectric constant are observed above -175 K for the two compounds.     

Preparation and the physical properties of antiperovskite-type compounds Cd1-xInxNNi3 (0≤x≤0.2) and Cd1-yCuyNNi3 (0≤y≤0.2)

Two series of Cd1-xInx NNi3(0 ≤x≤ 0.2) and Cd1-yCuyNNi3(0≤y≤0.2) samples were prepared from CdO, In2O3 , CuO, and nickel powders under NH3 atmosphere at 773K. The structural and physical properties were investigated by means of X-ray powder diffraction temperature-dependent resistivity and magnetic measurements. X-ray powder diffraction results showed that the Cd 1 x In x NNi 3 and Cd 1 y Cuy NNi 3 compounds have a typical antiperovskite structure, and the CdNNi3, Cd0.9 In 0.1 NNi3 , and Cd0.9Cu0.1NNi3 compounds show metallic temperature-dependent resistivity and exhibit a Fermi liquid behavior at low temperature. In contrast to the paramagnetism previously reported, the CdNNi 3 sample exhibits very soft and weak ferromagnetism, and no superconductivity was found in the Cd 1 x In x NNi 3 and Cd 1 y Cu y NNi 3 samples down to 2 K. Each sample exhibited very soft and weak ferromagnetism, and the temperature dependence of the magnetization of the Cd 1-xInx NNi 3 and Cd1-y Cu y NNi 3 samples can be well fitted to the combination of a Bloch term and a Curie–Weiss term.     

Structural distortions and magnetisms in Fe-doped LaMn1-xFexO3 （0 〈 x ≤0.6）

X-ray absorption spectra （XAS） at Mn K-edge and Fe K-edge in LaMnl-xFexO3 show that with the increase of Fe substitution the chemical valence of Mn4＋ decreases, while the chemical valence of Fe3＋ remains unchanged. Structural distortions, such as the rotating and tilting for oxygen octahedron in the unit cell vary with iron content. A phase transition occurs at the Fe content values of 0.2~0.3. The evolutions of rotation and tilting angle of FeO6/MnO6 octahedral may be the vital factors to the structure and magnetism. We believe that the spin configuration of Fe3＋ may vary from the intermediate spin t2g4eg1 （S = 3/2） to the higher spin t2g3eg2 （S = 5/2） near the phase transition.     

Preparation and the physical properties of antiperovskite-type compounds Cd_1-xIn_x NNi₃（0 ≤x≤ 0.2） and Cd_1-yCu_yNNi₃（0≤y≤0.2）

Two series of Cd1-xInx NNi3(0 ≤x≤ 0.2) and Cd1-yCuyNNi3(0≤y≤0.2) samples were prepared from CdO, In2O3 , CuO, and nickel powders under NH3 atmosphere at 773K. The structural and physical properties were investigated by means of X-ray powder diffraction temperature-dependent resistivity and magnetic measurements. X-ray powder diffraction results showed that the Cd 1 x In x NNi 3 and Cd 1 y Cuy NNi 3 compounds have a typical antiperovskite structure, and the CdNNi3, Cd0.9 In 0.1 NNi3 , and Cd0.9Cu0.1NNi3 compounds show metallic temperature-dependent resistivity and exhibit a Fermi liquid behavior at low temperature. In contrast to the paramagnetism previously reported, the CdNNi 3 sample exhibits very soft and weak ferromagnetism, and no superconductivity was found in the Cd 1 x In x NNi 3 and Cd 1 y Cu y NNi 3 samples down to 2 K. Each sample exhibited very soft and weak ferromagnetism, and the temperature dependence of the magnetization of the Cd 1-xInx NNi 3 and Cd1-y Cu y NNi 3 samples can be well fitted to the combination of a Bloch term and a Curie–Weiss term.     

The doping effects of BiFe1-xCoxO3 （x=0.0-0.8） in layered perovskite BiaTi3O12 ceramics

BisFe1-xCoxTi3O15 （x=0.0, 0.2, 0.4, 0.5, 0.6, and 0.8） multiferroic ceramics are synthesized in two steps using the solid state reaction technique. X-ray diffraction patterns show that the samples have four-layer Aurivillius phases. At room temperature （RT）, the samples each present a remarkable coexistence of ferromagnetism （FM） and ferroelectricity （FE）. The remnant polarization （2Pr） reaches its greatest value of 14 gC/cm2 at x = 0.6. Remnant magnetization （2Mr） first increases and then decreases, and the greatest 2Mr is 7.8 menu/g when x = 0.5. The magnetic properties for x = 0.4 are similar to those for x = 0.6, indicating that the magnetic properties originate mainly from the coupling between Fe3＋ and Co3＋ ions, rather than from their own magnetic moments.     

Doping effect on the structure and physical properties of quasi-one-dimensional compounds Ba_9Co_3(Se_(1-x)S_x)15(x=0–0.2)

A series of samples of Ba_9Co_3(Se_(1-x)S_x)15 (x=0,0.05,0.1,0.15,0.2) with quasi-one-dimensional (1D) structure were successfully synthesized under high-temperature and high-pressure conditions.The influence of partial substitution of S for Se on the structure,electronic transport,and magnetic properties of Ba_9Co_3(Se_(1-x)S_x)15 has been investigated in detail.The x-ray diffraction data shows that the lattice constant decreases linearly with increasing S-doping level,which follows the Vegrad’s law.The doped S atoms preferentially occupy the site of Se atoms in CoSe_6 octahedron.Physical properties measurements indicate that all the samples of Ba_9Co_3(Se_(1-x)S_x)15 are semiconducting and display spin glass behavior.As the replacement of Se by smaller size S,although the inter-chain distance decreases,the electronic hopping between CoSe/S_6 chains is weakened and leads to an increase of band gap from 0.75 e V to 0.86 e V,since the S-3p electrons are more localized than Se-4p ones.Ba_9Co_3(Se_(1-x)S_x)15 exhibits 1D conducting chain characteristic.     

Effects of BaCu（B2Os） addition on sintering temperature and microwave dielectric properties of BasNb4O15-BaWO4 ceramics

The effects of BaCu（B2Os） （BCB） addition on the microstructure, phase formation, and microwave dielectric proper- ties of BasNb4015-BaWO4 ceramic are investigated. As a sintering aid, BaCu（B2Os） ceramic could effectively lower the sintering temperature of BasNb4015-BaWO4 ceramic from 1100 ℃ to 950 ℃ due to the liquid-phase effect. Meanwhile, BaCu（B2Os） addition effectively improves the densification of BasNb4015-BaWO4 ceramic and significantly influences the microwave dielectric properties. X-ray diffraction analysis reveals that BasNb4015 and BaWO4 coexist with no crystal phase of BaCu（B2Os） in the sintered ceramics. The BasNb4015-BaWO4 ceramics with 1.0 wt% BaCu（B2Os） sintered at 950 ℃ for 2 h presents good microwave dielectric properties of er = 19.0, high Q× f of 33802 GHz and low vf of 2.5 ppm/℃.     

Growth and optical properties of Cr~（3＋）-doped CdWO_4 single crystals

A high-quality Cr 3+:CdWO4 single crystal at a size of approximatelyΦ25×80 mm is grown using the Bridgman method with CdO,WO3,and Cr2O3 as raw materials and their molar ratio of 100:100:0.5.The temperature gradient of solid-liquid interface at growth is approximately 50?C/cm and the growth rate is 0.05 mm/h.The X-ray diffraction(XRD),absorption,excitation,and emission spectra of different parts of the as-grown and O2-annealed crystals are investigated.Two strong broad optical absorption bands of about 472 and 708 nm are observed,and they are associated with the transitions 4 A2→ 4 T1 and 4 A2→ 4 T2.The weak 4 T2→ 2 E transition(the R-line)at 632 nm is also observed.The crystal-field parameter Dq and the Racah parameters B and C are estimated to be 1 412.4,776.8,and 3 427.6 cm? 1,respectively,according to the absorption spectra and crystal-splitting theory.A broadband fluorescence at about 1 000 nm due to 4 T2→ 4 A2 transition is produced by exciting the samples at 675 nm.After being annealed in an O2 atmosphere,the crystals become more transparent,while the effective light absorption of Cr 3+ ions is evidently enhanced and the emission intensity is also strengthened due to the reduction of oxygen vacancies in the CdWO4 crystal after annealing.     

Multiferroic properties and exchange bias in Bi1-xSrxFeO3 （x = 0-0.6） ceramics

Multiferroic properties and exchange bias(EB) in Bi1-xSrxFeO3(x = 0–0.6) ceramics synthesized by a modified Pechini method are investigated. Sr concentration dependence of structure distorting, ferroelectric properties, and dielectric properties were studied at room temperature. Appropriate Sr doping(x = 0.05–0.2) has been found to decrease the conductivity, enhance ferroelectric properties and give rise to high dielectric constant. Compared with antiferromagnetic BiFeO3 compound, BSFO-x(0 ≤ x ≤ 0.4) ceramics show weak ferromagnetism at room temperature, and their exchange bias field and vertical magnetization shift are observed and exhibit a strong dependence on the content of Sr. This observed EB effect which keeps stable in BSFO ceramics at 10 K tend to vanish at room temperature with Sr concentration over 0.4.     

Doping effects on structural and magnetic evolutions of orthoferrite SmFe（1-x） Alx O3

The structural and magnetic properties of SmFeO3 with B site substitution of non-magnetic atom A1 are investigated. The x-ray diffraction patterns show that SmFe（1-x）AlxO3 remains an orthorhombic structure within the whole doping range, and the unit-cell volume decreases monotonically with the increase of doped A1 concentration. Besides, the octa- hedral tilting distortions of FeO6 are found to be alleviated while the tolerance factor increases. However, the relationship between the lattice parameters and Al concentration is observed to deviate from Vegard＇s rule, and this may be caused by magnetostriction effects. For the doping content values in a range 0 〈 x 〈 0.6, the ferromagnetism, antiferromagnetism, and paramagnetism are observed to occur continuously. Moreover, the magnetization and the spin reorientation temperature （Tk） decrease monotonically as Al content value increases. With the doping content values being x = 0.8 and 1.0, these compounds only show paramagnetic behavior.     

Magnetic properties and magnetostriction of PrxNd1-xFe1.9（0≤x≤1.0） alloys at low temperature

The crystal structure,magnetic and magnetostrictive properties of high-pressure synthesized Prx Nd1-xFe1.9(0≤x≤1.0) alloys were studied.The alloys exhibit single cubic Laves phase with MgCu 2-type structure.The initial magnetization curve reveals that Pr0.2Nd0.8Fe1.9 has a minimum magnetocrystalline anisotropy at 5 K.The magnetostriction curve at 5 K shows that Pr0.2Nd0.8Fe1.9 has a very good low-field magnetostrictive property,and the magnetostriction of the PrxNd1-xFe1.9 alloy in high magnetic field is attributable mainly to Pr.The temperature dependence of the magnetostriction(λ ||) at the field of 5 kOe shows that the substitution of Nd reduces the K 1 remarkably,and the values of λ|| of Pr0.2Nd0.8Fe1.9 and Pr0.8Nd0.2Fe1.9 alloys are nearly five times larger than that of the PrFe 1.9 alloy below 50 K;the λ|| of Pr0.8Nd0.2Fe1.9 reaches up to 1082 ppm at 100 K,which makes it a potential candidate for application in this temperature range.     

A density functional theory study of the electronic structures and magnetic properties of Fe（1-x）Cox alloy nanowires encapsulated in （10,0） carbon nanotubes

Under the generalized gradient approximation, the electronic structures and magnetic properties of Fe_(1-x)Co_x alloy nanowires encapsulated inside zigzag (10,0) carbon nanotubes (CNTs) are investigated systematically using firstprinciple density functional theory calculations. For the fully relaxed Fe_(1-x)Co_x/CNT structures, all the C atoms relax outwards, and thus the diameters of the CNTs are slightly increased. Formation energy analysis shows that the combining processes of all Fe_(1-x)Co_x/CNT systems are exothermic, and therefore the Fe_(1-x)Co_xalloy nanowires can be encapsulated into semiconducting zigzag (10,0) CNTs and form stable hybrid structures. The charges are transferred from the Fe_(1-x)Co_xnanowires to the more electronegative CNTs, and the Fe-C/Co-C bonds formed have polar covalent bond characteristics. Both the spin polarization and total magnetic moment of the Fe_(1-x)Co_x/CNT system are smaller than those of the corresponding freestanding Fe_(1-x)Co_xnanowire, and the magnetic moment of the Fe_(1-x)Co_x/CNT system decreases monotonously with increasing Co concentration, but the Fe_(1-x)Co_x/CNT systems still have a large magnetic moment, implying that they can be utilized in high-density magnetic recording devices.     

Structures,stabilities, and electronic properties of F-doped Sin （n=1～12） clusters：Density functional theory investigation

The geometries, stabilities, and electronic properties of FSin （n=1～12） clusters are systematically investigated by using first-principles calculations based on the hybrid density-functional theory at the B3LYP/6-311G level. The geometries are found to undergo a structural change from two-dimensional to three-dimensional structure when the cluster size n equals 3. On the basis of the obtained lowest-energy geometries, the size dependencies of cluster properties, such as averaged binding energy, fragmentation energy, second-order energy difference, HOMO–LUMO （highest occupied molecular orbital–lowest unoccupied molecular orbital） gap and chemical hardness, are discussed. In addition, natural population analysis indicates that the F atom in the most stable FSin cluster is recorded as being negative and the charges always transfer from Si atoms to the F atom in the FSin clusters.     

First-principles study on the structure,electronic and magnetic properties of HoSin （n=1-12, 20） clusters

The structure, electronic and magnetic properties of HoSin（n= 1 - 12, 20） clusters have been widely investigated by first-principles calculation method based on density flmctional theory （DFT）. From our calculation results, we find that for HoSin（n=1- 12） clusters except n = 7.10, the most stable structures are a replacement of Si atom in the corresponding pure Sin＋1 clusters by Ho atom. The doping of Ho atom makes the stability of Si clusters enhance remarkably, and HoSin（n = 2, 5, 8, 11） clusters are more stable than their neighboring clusters. The magnetic moment of Ho atom in HoSin （n = 1 - 12, 20） clusters mainly comes from of electron of tto, and never quenches.     

Structure and magnetic properties of the intermetallic La2Co17−xMox (x=0.5, 1, 1.5, 2) and La2Co16−yFeyMo (y=0, 1, 2, 3, 4, 6) compounds

The effect of Mo and Fe atoms on the crystal structure and magnetic properties of the intermetallic La₂Co_17−xMo_x (x=0.5, 1, 1.5, 2), and La₂Co_16−yFe_yMo (y=0, 1, 2, 3, 4, 6) compounds have been studied by X-ray diffractometry, magnetic measurements and Mössbauer spectroscopy. All samples belong to the rhombohedral Th₂Zn₁₇-type structure and their lattice parameters a and c increase both with Mo and Fe content. From the La–Co–Mo samples only the one with x=0.5 presents planar anisotropy, whereas from the La–Co–Fe–Mo samples only the y=1 has uniaxial anisotropy. The magnetization M_S and the Curie temperature T_C decrease upon Mo substitution, whereas the anisotropy field H_A does not change significantly. In the Fe-substituted compounds M_S increases, but the Curie temperature increases slightly for 0⩽y⩽4 but decreases in y=6. The low temperature M–T curve shows that the samples La₂Co_16.5Mo_0.5, and La₂Co₁₀Fe₆Mo present a spin reorientation transitions at 70 and 260 K, respectively. Mössbauer samples were obtained for all Fe-containing samples in the temperature range 20–300 K. Above 260 K a jump in the values of the hyperfine fields and quadrupole splitting parameters is observed which can be associated to the spin reorientation.     

Analytical potential energy function for the electronic states 2^∏1/2 and 2^∏3/2 of O^x2 （x=＋1, -1）

The splitting of potential energy levels for ground state X^2∏g of O^x2 （x = ＋1,-1） under spin-orbit coupling （SOC） has been calculated by using the spin-orbit （SO） multi-configuration quasi-degenerate perturbation theory （SO-MCQDPT）. Their Murrell-Sorbie （M S） potential functions are gained, and then the spectroscopic constants for electronic states 2^∏1/2 and 2^∏3/2 are derived from the M S function. The vertical excitation energies for O^x2 （x = ＋1,-1） are v[O2＋1^（2∏3/2→X^2∏1/2）] =195.652cm^-1, and v[O2^-1（2^∏1/2 →X^2∏3/2）] =182.568cm^-1, respectively. All the spectroscopic data for electronic states 2^∏1/2 and 2^∏3/2 are given for the first time.     

The crystal structures and physical properties of the solid solution compound Ba₅Y_8-xMn₄O_21-1.5x（x = 0,1）

New oxometallides with the formula Ba5Y8 xMn4O21 1.5x(x = 0,1) are prepared through an atmospherecontrolled solid-state reaction.Two single-phase samples with Ba/Y/Mn atomic ratios 5/8/4(Y8) and 5/7/4(Y7) are obtained.The crystal structures and the physical properties of the compounds are investigated by X-ray powder diffraction,magnetization,conductivity,and dielectricity measurements.The Ba5Y8 xMn4O21 1.5x compound is demonstrated to be a Y-deficient solid solution.The solid solution compound Ba5Y8 xMn4O21 1.5x crystallizes into tetragonal symmetry with the space group I4/m.Detailed structure analysis by Rietveld refinement of the X-ray powder diffraction data reveals that the Y vacancies occur preferentially at the Y(2) site.Thermal magnetization measurements indicate the presence of antiferromagnetic interaction between Mn ions in the compounds,and temperature-dependent resistivity measurements show that insulator-semiconductor transitions occur around 175 K and 170 K for the Y8 and Y7 samples,respectively.Strong frequency dependences of the dielectric constant are observed above ～175 K for the two compounds.