Structural, transport, magnetic, and dielectric properties of La1−x Te x MnO3 (x = 0.10 and 0.15)

In this study, we have investigated the structure, temperature-dependent resistivity, magnetization, and dielectric properties of La_1?x Te _x MnO_3±δ (x = 0.10 and 0.15). X-ray diffraction analysis confirms the rhombohedral crystal symmetry with space group R $ \overline{3} $ c. For both the samples, the temperature dependence of magnetization plots show paramagnetic-to-ferromagnetic phase transition. The Curie temperature (T _c) and magnitude of magnetization increase with the Te concentration. Field-dependent magnetization produces the asymmetric hysteresis loop that has been attributed to the magneto crystalline anisotropy induced by lattice distortion and the rare earth spin coupling at room temperature. Temperature-dependent resistivity plots exhibit metal–insulator transition (MIT) and charge-ordering state. These plots have been fitted using variable range hopping model, and the density of states [N(E_F)] has been estimated. Magnetoresistance is measured as a function of temperature in the field of 1T, 5T, and 8T. The dielectric constant shows an anomaly near MIT. The dielectric constant exhibits a peaking behavior with the applied frequency and the temperature dependence of dielectric constant attains colossal values at high temperatures.     

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.     

Structural,morphological and opto-electric properties of Y2−xYbxO3 (x = 0.0, 0.04, 0.08, 0.12) nanopowders for laser host ceramic material applications

Journal of Materials Science: Materials in Electronics - Rare Earth substituted Sesquioxides compounds, specially Yttria (Y2O3) are essential ceramic materials for solid-state lasers,...     

Ionic conductivity in the ternary system (ZrO2)1−0.08x−0.12y–(Y2O3)0.08x–(CaO)0.12y

The total electrical conductivity of the samples in the ternarysystem (ZrO₂)_{1-0.08x-0.12y} –(Y₂O₃)_0.08x –(CaO)_0.12y was measured by adirect current four-probe method in the temperature range 773 to1673 K. It was found that partial replacement of Y₂O₃ by CaO in thesystem ZrO₂–Y₂O₃ may enhance the electrical conductivity at highertemperatures. At lower temperatures, however, doping CaO as the thirdcomponent into the system ZrO₂–Y₂O₃ depresses the conductivity. Theobserved mixed dopant effect was then analyzed by considering thecombined effect of both parameters appeared in the traditionalArrhenius equation, the activation energy, E, and the preexponentialfactor, ₀, on the temperature-dependence of the measured conductivity.     

Magneto-transport and Magnetic Susceptibility of SmFeAsO1−x F x (x=0.0 and 0.20)

We report superconductivity in the SmFeAsO_1?x F _x for the x=0.2 system being synthesized using the single step solid state reaction route. Rietveld analysis of room temperature X-ray diffraction (XRD) data shows the studied samples, SmFeAsO_1?x F _x with x=0.0 and x=0.2, are crystallized in a single phase tetragonal structure with space group P4/nmm. The resistivity measurement shows superconductivity for the x=0.20 sample with T _c (onset) ～51.7 K. The upper critical field, [H _c2(0)] is estimated ～3770 kOe by Ginzburg–Landau (GL) theory. Broadening of superconducting transition in magnetotransport is studied through thermally activated flux flow in an applied field up to 130 kOe. The flux flow activation energy (U/k _B ) is estimated ～1215 K for 1 kOe field. Magnetic measurements exhibited bulk superconductivity with lower critical field (H _c1) of ～1.2 kOe at 2 K. In the normal state, the paramagnetic nature of compound confirms no trace of magnetic impurity, which orders ferromagnetically. AC susceptibility measurements have been carried out for SmFeAsO_0.80F_0.20 sample at various amplitude and frequencies of applied AC drive field. The intergranular critical current density (J _c ) is estimated. Specific heat [C _p (T)] measurement showed an anomaly at around 140 K due to the SDW ordering of Fe, followed by another peak at 5 K corresponding to the antiferromagnetic (AFM) ordering of Sm⁺³ ions in the SmFeAsO compound. Interestingly, the change in entropy (marked by the C _p transition height) at 5 K for Sm⁺³ AFM ordering is heavily reduced in the case of the superconducting SmFeAsO_0.80F_0.20 sample.     

Study and Characterization of （KxSr1-x）CrOz,x = 0.10-0.50System

Studies of thermodynamic, electric and magnetic properties were conducted on the （KxSr1-x）CrOz, x = 0.10, 0.15 and 0.50system; adjusted for different crystal si...     

Structural, Electronic and Magnetic Properties of Zinc-Blende Ga1−x TM x N (TM = Cr, Mn, Fe, V)

In this paper, we present a theoretical study of structural, electronic and magnetic properties for zinc-blende Ga_1?x TM _x N(TM = Cr, Fe, Mn, V) using the full-potential augmented plane wave (FP-APW) method with local-spin density approximation (LSDA). We have analysed the dependence of structural parameters values on the composition x in the range of x=0.25, x=0.50. Also, the role of p–d hybridisation is analysed by partial (PDOS) and total density of states (TDOS). The magnetic moment of Ga_1?x TM _x N has been studied by increasing the concentration of TM atom. The TM atom is the most important source of the total magnetic moment in these alloys, while the contributions from Ga and N are minor. In addition our results verify the half-metallic ferromagnetic character of TM doped GaN.     

The Structural, Magnetic Susceptibility, and Raman Spectroscopy Study of CuRh1−x Co x O2 (0≤x≤0.05) Delafossite Compounds

In the layered structure of delafossite-type metal oxides AMO₂, the M position can be occupied by a wide spectrum of trivalent or couples of divalent/tetravalent cations. In the A position, however, only monovalent, linearly coordinated cations are accommodated. This study focuses on CuRh_1?x Co _x O₂ (0≤x≤0.05) polycrystalline samples which are prepared by solid-state reaction method. Magnetic susceptibility measurements of all samples were done in a temperature range 2–250 K. The interaction of the M cations with each other through M–O–M linkages of approximately 180° is expected to be the dominant consideration, and this would be paramagnetic in nature. The composition-dependent Raman spectra of CuRh_1?x Co _x O₂ displayed three intense modes (670 cm^?1, 490 cm^?1, and 204 cm^?1) at room temperature, which matched with other delafossite structures.     

First-Principle Calculations of Structural,Electronic, and Magnetic Properties of Cubic Al1−x TM x N (TM = V,Cr, Mn,Fe)

We investigate the structural, electronic, and magnetic properties of zinc-blende diluted magnetic semiconductors (DMS) Al _1?x TM _x N for transition metals (TM) = V, Cr, Mn, and Fe at x = 0.125 and 0.25, using first-principle calculations with the full-potential linearized augmented plane wave (FP-LAPW) method within the density functional theory and local spin-density approximation, in an aim to predict properties of Al _1?x TM _x N compounds. We have analysed the reliance of structural parameter values on the composition x in the range of x= 0.125?0.25. Results of calculated electronic structures reveal that Al _1?x TM _x N have stable ferromagnetic ground state and they are ideal half-metallic (HM) ferromagnetic at their equilibrium lattice constants. We have also studied the magnetic moment of Al _1?x TM _x N by increasing the concentration of TM atom; this is the most important source of the total magnetic moment in these alloys, while the contributions from Al, N, and interstitial moments are minor.     

Study of Electronic and Magnetic Properties of Zn1−x M x O (M = Mn and Cr) by ab initio Calculations

The electronic structure and ferromagnetic properties of Zn_1?x M _x O (M = Mn and Cr) have been investigated by using the Korringa–Kohn–Rostoker (KKR) method combined with the coherent potential approximation (CPA). The half-metal behavior is observed for different doping concentrations. The gap energies are deduced for different dilution x values. The magnetic moment of each atom and the total magnetic moment are computed. A special attention is paid to the discussion of the mechanism of ferromagnetism in these components.     

Enhancement of Magnetic and Dielectric Properties in Chemically Modified Multiferroic (0.90)BiFe1−x Cr x O3–(0.10)BaTiO3 Nanocomposite

Multiferroic BiFeO₃ and Cr-doped (0.90)BiFe_1?x Cr _x O₃–(0.10)BaTiO₃ (x=0.00, 0.03, and 0.05) nanocomposites were prepared by sol–gel method. Optimum calcination and sintering strategies for obtaining pure perovskite phase have been determined. X-ray diffraction and transmission electron microscope (TEM) were used for the structural and particle size analysis, whereas LCR and SQUID magnetometer was used for dielectric and magnetic measurements. TEM measurements show that the average particle sizes of all the samples were ～19 nm. The dielectric constant was found to be increased twofold in low frequency region with the Cr-doping for x=0.05 in (0.90)BiFe_1?x Cr _x O₃–(0.10)BaTiO₃. The hysteresis curve (M–H) exhibits ferromagnetic nature for all the samples (x=0.0, 0.03, and 0.05) and the spontaneous magnetization at room temperature was found to be 0.63 emu/gm in pure BiFeO₃, which increased to 0.99 emu/gm for x=0.05. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves show large discrepancy suggesting spin glass behavior.     

The Magnetic Properties of Mn x Fe1−x NiSi (x=0,0.25,0.5,0.75,1) Alloys

The magnetic properties of Mn _x Fe_1?x NiSi (x=0,0.25,0.5,0.75,1) alloys are studied using density functional theory and the WIEN2k package. The exchange correlation potential is treated by generalized gradient approximation (GGA). The total energy calculations of these alloys confirm the stability of the ferromagnetic phase as compared to a nonmagnetic phase. The total magnetic moment is not a linear function of x. By increasing x, it increases and then decreases. The peak position of the magnetic moment is near x=0.75.     

Effect of Ni Doping on Structural,Morphological, Optical and Magnetic Properties of Zn1−x Ni x O Dilute Magnetic Semiconductors

Ni²⁺-doped ZnO diluted magnetic semiconducting materials (Zn_1?x Ni _x O with x=0.01,0.02,0.03,0.04,0.05) were synthesised by the co-precipitation method. All synthesised samples were sintered at 600 °C for 6 hours. The effects of Ni²⁺ ion-doping on the structural, morphological, optical and magnetic properties of ZnO were investigated using powder X-ray diffraction, field emission SEM, UV–DRS spectroscopy, photoluminescence and vibrating sample magnetometry. The XRD patterns of pure and Ni-doped ZnO samples revealed single phase hexagonal wurtzite structure. The SEM analysis revealed the morphology of prepared samples, and the chemical compositions of all samples were analysed using exhibit energy density X-ray analysis (EDAX) characterisation. The absorption and emission properties revealed the effect of Ni²⁺ doping in ZnO samples. All Ni²⁺ ion-doped samples showed ferromagnetism at room temperature. The observed results are here analysed and reported.     

The Structural and Magnetic Properties of Zn0.8−4x Dy x O y (0.05≤x≤0.10) Compounds Prepared by Solid-State Reactions

In this study, Dy-doped ZnO (Zn_0.8?4x Dy _x O _y (0.05≤x≤0.10)) samples were prepared by the solid-state reaction method, and were characterized by using the XRD, SEM and EDX techniques. The SEM results clearly demonstrate that the grains of the samples are very well connected to each other and tightly packed. From the XRD and EDX spectra, it has been concluded that the substituting of Dy³⁺ for Zn²⁺ in ZnO causes almost no change in the hexagonal wurtzite structure of ZnO. However, the lattice parameters a and c of Dy-doped ZnO are slightly different from those of the pure ZnO. These observations may be due to the slightly different ionic sizes of Zn²⁺ and Dy³⁺ ions. Our magnetization measurements (M–H) and (M–T) show paramagnetic behavior with a negative value of the Curie–Weiss temperature, corresponding to an antiferromagnetic exchange coupling in Dy-doped ZnO. Since, for low magnetic fields the extrapolation of the H/M versus temperature curves cut the T axes at negative values, we believe that the substitution of Dy in ZnO causes an overwhelming antiferromagnetic interaction for x≤0.10.     

Investigations of Structural, Electronic, and Half-metallic Ferromagnetic Properties in (Al, Ga, In)1−x M x N (M = Fe, Mn) Diluted Magnetic Semiconductors

We investigate the structural, electronic, and magnetic properties of (M = Fe, Mn)-based zinc blende diluted magnetic semiconductors (DMS) (Al, Ga, In)_1?x M _x N for (x=0.0625,0.125,0.25), using first-principles calculations with the full-potential linearized augmented plane waves (FP-LAPW) method within the density functional theory and local spin-density approximation. The analysis of electronic structures and magnetic properties show that (Al, Ga, In)_1?x Fe _x N at (x=0.0625,0.125,0.25) are magnetic insulators, and In_1?x Mn _x N at (x=0.0625,0.125) are metallic in nature. On the other hand the (Al, Ga)_1?x Mn _x N at (x=0.0625,0.125,0.25) and In_0.75Mn_0.25N are half-metallic ferromagnets with magnetic spin polarization of 100 %, where the ferromagnetic ground states result from a double-exchange mechanism, and these compounds are predicted to be good candidates for spintronic applications.     

Structural and optical properties of Cd x Zn(1 − x)Te thin films

Seven Cd _x Zn_{(1 ? x} Te solid solutions with x = 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 were synthesized by fusing stoichiometric amounts of CdTe and ZnTe constituents in silica tubes. Each composition was used in the preparation of a group of thin films of different thicknesses. Structural investigation of the obtained films indicates they have a polycrystalline structure with predominant diffraction lines corresponding to (111) (220) and (311) reflecting planes, which can be attributed to the characteristics of growth with the (111) plane. The optical constants (the refractive index n, the absorption index k, and the absorption coefficient α) of Cd _x Zn_{(1 \s -x)} Te thin films were determined in the spectral range 500–2000 nm. At certain wavelengths it was found that the refractive index, n, increases with increasing molar fraction, x. It was also found that plots of α² (hv) and α^1/2 (hv) yield straight lines, corresponding to direct and indirect allowed transitions respectively obeying the following two equations: $$\begin{gathered} E_g^d = 1.583 + 0.277x + 0.197x^2 \hfill \\ E_g^{ind} = 1.281 + 0.111x + 0.302x^2 \hfill \\ \end{gathered}$$