Gd Substitution Effects on the Magnetic Properties of the Pr1−x Gd x Co4Si Compounds

The crystal structure and magnetic properties of single phase Pr_1?x Gd _x Co₄Si compounds with x=0,0.2,0.4,0.6,0.8, and 1.0 have been investigated. X-ray analysis reveals that the compounds crystallize as a single phase having the hexagonal CaCu₅-type structure with the space group P6/mmm. The substitution of Gd for Pr causes a linear decrease of the unit-cell parameters a and c, and the unit-cell volume V. Magnetic measurements indicate that all samples are ordered magnetically below the Curie temperature. The saturation magnetization at 4.2 K decreases upon the Gd substitution up to x=0.6, and then increases.     

The Effect of Cadmium Substitution on the Superconducting Properties of Tl1−x Cd x Ba2Ca2Cu3O9−δ Compound

In order to study how Cd substitution for Tl changes, the superconducting properties of Tl_1?x Cd _x Ba₂Ca₂Cu₃O_9?δ compound with x=0, 0.1, 0.2 and 0.3. We have prepared samples with Cd in place of Tl by the solid state reaction method. It has been found that the increase of the Cd concentrations of all samples produced increases the transition temperature from 113 to 123 K and changes the mass density ρ _m, C/a and volume fraction V _Ph(1223).. XRD shows that the partial substitution of Tl with Cd is helpful to form the superconducting 1223 phase (TlBa₂Ca₂Cu₃O_9?δ ). It has been shown that samples mainly contain tetragonal phase 1223 with a few additional mixed 1212 and 1201 phases.     

Thermal Properties of La1−x A x CoO3 (A = Ca and Ba)

The thermal properties of La_1?x A _x CoO₃ (A = Ca, Ba and 0.0≤x≤0.3) for temperature (1 K≤T≤300 K) have been investigated using the Modified Rigid ion model (MRIM) with pair wise interionic interaction potential. The temperature dependent (1 K≤T≤300 K) variation of specific heat and thermal expansion for La_1?x A _x CoO₃ (A = Ca, Ba and 0.0≤x≤0.3) has presented proper interpretation of the experimental data. Also the effect of lattice distortions on the thermal properties of these perovskite cobaltates has been studied by an atomistic approach. In addition, the results on the cohesive energy (?), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θ _D ) and Gruneisen parameter (γ) are also discussed.     

Magnetic Properties of the Ce(Pd1−x Cu x )3 System

CePd₃ is an intermediate valence compound with a variety of interesting electronic properties resulting from the partially filled f-shell electrons of cerium atom. Substitution on cerium site with Cu causes a dramatic change in the electronic behavior of the compound. In this work, Ce(Pd_1?x Cu _x )₃ system, 0 ≤ x ≤ 0.133, with x = 0, 0.017, 0.033, and 0.133, has been synthesized by arc melting method. The powder X-ray diffraction reveals that the compounds crystallize in AuCu₃-type structure where copper enters the lattice substitutionally. Magnetic susceptibility measurements as a function of temperature have been carried out on these alloys which show that with increasing copper content x, the alloys Ce(Pd_1?x Cu _x )₃ show a smooth crossover from the weak temperature dependence of CePd₃ to a Curie-Weiss behavior for higher concentrations of x. The value of μ _eff increases with x, while the paramagnetic Curie temperature shows a large reduction with increase in x; this suggests a very rapid decrease in the Kondo temperature with x.     

Viscosity of Fe90B x Si(10 − x) melts

High Temperature - The temperature dependences of the viscosity of liquid Fe90B x Si(10 − x) alloys are studied in the mode of heating and subsequent cooling. The temperature dependences of...     

Effect of electropulsing on the precipitation of NbC x N1−x from austenite phase

The precipitation of NbC _x N_1?x significantly affects the high-temperature mechanical properties of Nb microalloyed steel. The control of the precipitation behaviour of NbC _x N_1?x is the key, especially the nucleation and precipitation from Nb solid solution. We explore to use electropulsing to promote the precipitation of NbC _x N_1?x through thermodynamic model, chemical phase analysis, XRD and TEM. The modelling research show that electropulsing intensity significantly promotes the nucleation of NbC _x N_1?x in austenite phase. The higher the electropulsing temperature is, the better the promotion effect is. The chemical phase analysis and XRD investigation results show that electropulsing can increase the amount of precipitation of NbC _x N_1?x by 50% at 950°C compared to the precipitation without electropulsing.     

Effect of Pr and Ca Substitution on the (La1−x−u Pr x Ca u )(Ba1.5Sr0.5)Cu3O y Superconductors

In the fully oxygenated single phase (La_1–x–u Pr _x Ca _u )(Ba_1.5Sr_0.5)Cu₃O _y (0x1.00, 0u0.20) system, if u=0, the z-coordinate of the Ba site, z(Ba), and d _Ba–bp (distance between the Ba site and the basal plane) are lowered by increasing the amount of Pr in the (La_1–x Pr _x )(Ba_1.5Sr_0.5)Cu₃O _y series. On the contrary, if u0, z(Ba) and d _Ba–bp are raised by increasing the amount of Ca ion in the (La_1–x–u Pr _x Ca _u )(Ba_1.5Sr_0.5)Cu₃O _y (0x0.30, 0u0.20) series. Linear relationships are found between z(Ba), d _Ba–bp and the oxygen stoichiometry (y). T _c and p _sh (the hole concentration in CuO₂ layers) increase with increasing the angle of Cu(2)-Ba-Cu(2). Relative positions of the Cu(2) and Ba sites are important in determining the T _c of these 123 compounds.     

Effect of Composition Variations on Electrical and Optical Properties of La1−x (Ca, Sr) x MnO3 Thin Films

Thin films of La _0.67 Ca _0.33 MnO ₃₊ (d 200 nm) grown at 750° C on MgO(100) substrates by pulsed laser deposition were annealed in various oxygen atmospheres. The LaF ₃ , CaF ₂ and Mn overlayers (d 5-10 nm) have been evaporated onto the films in order to saturate the compound by La, Ca or Mn during subsequent annealing at 900° C in air. Further, the pulsed injection CVD method has been utilized to prepare series of La _1–x Sr _x MnO ₃ films with x = 0÷0.5 on LaAlO ₃ (100). The effect of composition variations on electrical resistivity and magnetoresistance of the films as well as on their optical transmission and reflection spectra in the energy range between 0.2 and 4.0 eV has been investigated.     

Low-temperature properties of pseudoternary R(Rh1−x Ir x )4B4 (R=Ho and Dy) systems

Pseudoternary Ho(Rh_1–x Ir_x)₄B₄ and Dy(Rh_1–x Ir_x)₄B₄ systems were investigated with respect to the interplay between superconductivity (SC) and long-range magnetic ordering by means of specific heat (C) and upper critical magnetic field (H _c2) measurements. For Ho(Rh_1–x Ir_x)₄B₄ withx0.2 and Dy(Rh_1–x Ir_x)₄B₄ withx0.15, ferromagnetic (FM) ordering, reminiscent of spin-1/2 mean-field theory, was observed. In particular, FM ordering in Ho(Rh_1–x Ir_x)₄B₄ with 0.07x0.2 was found to destroy SC at a second critical temperatureT _c2 below the superconducting transition temperatureT _c, and was accompanied by a spike-shaped feature inC atT _c2. Coexistence of antiferromagnetic (AFM) ordering with SC was observed in both systems for 0.2x0.7. The compounds withx0.5 exhibited Néel temperaturesT _N that were smaller thanT _c and enhanced values ofH _c2 belowT _N. TheT _c andT _N undergo an abrupt decrease and increase, respectively, nearx0.5, and then cross atx0.6, above whichT _N>T _c. For Ho(Rh_1–x Ir_x)₄B₄ with 0.275x0.4, two different AFM transitions were detected in a double-peak feature inC.     

Thermal Diffusivity of La1−x Sr x MnO3 (x < 0.3)

Perovskite manganites are interesting because of their colossal magnetoresistance. In this work high resolution thermal diffusivity measurements of La_1–x Sr _x MnO₃ (0 x 0.3) single crystals in the temperature range from 250 to 400 K are presented. A photopyroelectric device in the standard back configuration has been used. The thermal diffusivity through second-order magnetic phase transitions, as well as through first- and second-order structural phase transitions has been measured. The critical parameters of the sample with x = 0.3 at the ferromagnetic-to-paramagnetic transition have been obtained, and are close to the values predicted by the Ising model.     

The Effect of Annealing Temperature on the Magnetic Properties of Mn x Co1?x Fe2O4 Ferrites Nanoparticles

Mn _x Co_1?x Fe₂O₄ ferrites compounds (0??x??0.6) have been synthesized by a glycol-thermal method from high-purity metals chlorides. Single phase spinel structure of the nanoparticles has been confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The diameters of the as-prepared powders were estimated from XRD and TEM and were found to be in the range: 7 to 13?nm. Room temperature magnetizations were obtained using a vibrating sample magnetometer (VSM) on the as-prepared samples and on samples annealed at 500 and 700?°C. The variation of coercive fields, saturation and remnant magnetizations as a function of composition (x) and grain size have been investigated. ⁵⁷Co M?ssbauer spectra for as-prepared samples were also measured at different temperatures (27, 100, and 200?°C). Significant changes in magnetization properties and M?ssbauer parameters are observed across the composition range studied. The variation of coercive fields and saturation magnetizations appear to critically depend on the particle sizes as the compounds evolve from single domain to multidomain structure.