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Semiconducting oxides that start functioning as superconductors in their glass ceramic phases are studied over a wide range of temperatures and frequencies to show that the universal power-law behavior is applicable to most of these glasses. In low temperatures and at high frequencies, there is minimal deviation from this limiting behavior for some glass compositions.

Polycrystalline multiferroic La0.8Bi0.2Fe1-xMnxO3 (0.0≤x≤0.4) samples were synthesized by the conventional solid state reaction method. Reitveld refinement of the x-ray diffraction patterns confirms the single phase character of all the compositions with orthorhombic structure having space group Pnma (No. 62). Dielectric properties of the samples at temperatures 200–475 K and frequencies 500 kHz–1 MHz authenticate the stabilization of ferroelectric phase with Mn substitution. Dielectric responses of these multiferroics have been analyzed carefully, in the light of “universal dielectric response” model. While cooling from room temperature to 20 K, systematic shifts in magnetization hysteresis loops indicate the presence of exchange bias (EB) phenomenon in the system. Magnetic behavior of these samples has been briefly discussed on the basis of “EB” model for granular systems. Temperature and magnetic field dependent magnetization data demonstrate enhanced magnetization due to the Mn substitution. Magnetocapacitance measurement reveals the magnetoelectric coupling for wide range of temperature (180–280 K) and decrease in dielectric loss at high magnetic field (3 T). [ABSTRACT FROM AUTHOR]

We present here the magnetic, dielectric, and electronic structural properties of Ti doped BiMn2O5 multiferroic materials. The x-ray diffraction (XRD) studies of BiMn2-xTixO5 (0≤x≤0.5) indicate no structural change up to x=0.5, though the lattice parameters (a and c) increase with increasing value of x. Dielectric constant and magnetization data show the evolution of new dielectric anomalies at ∼120 K and weak magnetic feature at ∼86 K with the Ti substitution compared to that of undoped one. However, Ti replacement vanishes the ferroelectric transition of BiMn2O5 at ∼35 K and gradually suppresses the antiferromagnetic ordering at ∼39 K. Polarization of Bi 6s2 lone pair electrons is attributed to the reason behind new dielectric anomalies, whereas new weak magnetic feature at ∼86 K is attributed to strong spin-phonon coupling. X-ray absorption spectroscopy (XAS) studies on O K, Mn K, L3,2, and Ti L3,2 edges of BiMn2-xTixO5 samples along with the reference compounds have been performed and compared to bestow the exact chemical states of functioning ions. The Ti L-edge spectra clearly indicate the substitution of Ti4+ ions in all samples. XRD as well as XAS data and increase in net magnetic moment coherently indicate the replacement of Mn4+ by Ti4+. [ABSTRACT FROM AUTHOR]

We present here the magnetic, dielectric, and electronic structural properties of Ti doped BiMn2O5 multiferroic materials. The x-ray diffraction (XRD) studies of BiMn2-xTixO5 (0≤x≤0.5) indicate no structural change up to x=0.5, though the lattice parameters (a and c) increase with increasing value of x. Dielectric constant and magnetization data show the evolution of new dielectric anomalies at ∼120 K and weak magnetic feature at ∼86 K with the Ti substitution compared to that of undoped one. However, Ti replacement vanishes the ferroelectric transition of BiMn2O5 at ∼35 K and gradually suppresses the antiferromagnetic ordering at ∼39 K. Polarization of Bi 6s2 lone pair electrons is attributed to the reason behind new dielectric anomalies, whereas new weak magnetic feature at ∼86 K is attributed to strong spin-phonon coupling. X-ray absorption spectroscopy (XAS) studies on O K, Mn K, L3,2, and Ti L3,2 edges of BiMn2-xTixO5 samples along with the reference compounds have been performed and compared to bestow the exact chemical states of functioning ions. The Ti L-edge spectra clearly indicate the substitution of Ti4+ ions in all samples. XRD as well as XAS data and increase in net magnetic moment coherently indicate the replacement of Mn4+ by Ti4+. [ABSTRACT FROM AUTHOR]

We report the x-ray absorption studies on O K, Fe L3,2, Ni L3,2, and Pr M5,4 edges in PrFe1-xNixO3 along with their structural, electrical transport, and magnetization characterizations. All the samples are in single phase having orthorhombic structure with space group Pnma for x≤0.4. Ni doping at Fe site brings the system in the conducting regime, resistivity decreases from GΩ cmto 260 mΩ cm at room temperature, and the magnetic ordering is stabilized. The temperature dependent resistivity follows the semiconducting behavior and fits well with Greaves’ variable range hopping model. The gap parameter is reduced from 2 to 0.118 eV. The materials are in weak ferromagnetic state and magnetization is gradually decreasing with the enhancement of Ni substitution, whereas magnetic anisotropy is reduced substantially. A new feature about 2.0 eV lower than the pre-edge of PrFeO3 in O K edge is observed with Ni substitution at Fe site due to the 3d contraction effect and is growing with the increase of Ni substitution. From 2p edges (L3,2 edges) of Fe and Ni, it is confirmed that both are in trivalent state and Ni is in mixed spin state with 3d7 (t2g5,eg2 and t2g6,eg1) configuration in ground state. The trivalent state of Pr is confirmed by x-ray absorption spectroscopy of Pr at M5,4 edges. These observations have been explained on the basis of charge carrier doping in PrFeO3 with the Ni substitution. The disorder induced localization is found to control the conductivity and magnetism in the present materials. The controlled doping of carriers in semiconducting regime and ferromagnetism propose these materials as a promising candidate for the spintronic applications. [ABSTRACT FROM AUTHOR]

Influence of TiO2 and ZnO oxides has been investigated elaborately on the conductivity and dielectric properties of unconventional and technologically important 40CuO–40Bi2O3–20X (where X=TiO2 and ZnO) glasses. The dc electrical conductivity of ZnO containing glass is found to be higher than that of TiO2 containing one at all temperatures (300–600 K). A change from adiabatic to nonadiabatic small polaron hopping conduction is observed due to the influence of TiO2 and ZnO oxides. It has been perceived that the ZnO doped glass shows relatively more ac conductivity compared to that of the TiO2 doped one, consistent with the dc conductivity data. Random-free-energy barrier model of Dyre [J. Appl. Phys. 64, 2456 (1988)] is suited to be the most appropriate one for explaining the frequency dependence of ac conductivity data and frequency exponent. The large dielectric constant in both the glasses can be explained by the response of Bi3+ ions to ac. [ABSTRACT FROM AUTHOR]

Partial substitution of Cu by K in multicomponent glassy precursor for high T[SUBC] superconductor viz. Bi[SUB2-x]Pb[SUBx]Sr[SUB2]Ca[SUB2]Cu[SUB3]O[SUBδ](x=0.1-0.3) is found to destroy superconductivity of the corresponding annealed phase. These glasses viz. Bi[SUB2-x]Pb[SUBx]Sr[SUB2]Ca[SUB2]Cu[SUB3-y]K[SUBy]O[SUBz](x=0.1-0.3, y=0.2), however, show ferroelectric transitions (between 500 and 530 K depending on x). The corresponding K free glasses are not ferroelectric but they are good precursors for high T[SUBC] superconductor. Nanocrystalline particles/clusters (∼10-50 nm size) embedded in the K doped glasses, observed from transmission electron microscopic studies, are considered to be responsible for the ferroelectric behavior of the bulk glass nanocrystal composite (GNC). Unlike K free glasses, the K-containing glasses do not become superconductor by annealing them at higher temperature. This indicates suppression of superconductivity by the precipitation of ferroelectric nanoparticles in the K doped GNC. Though their dielectric behavior is different, both the K free and K containing glassy systems are semiconductors and follow the similar nonadiabatic small polaron hopping conduction mechanism (obeying Holstein condition). A comparative study of the properties of the two glassy systems showing distinguishing behavior has been made. [ABSTRACT FROM AUTHOR]

Polycrystalline multiferroic [La.sub.0.8][Bi.sub.0.2][fe.sub.1-x][Mn.sub.x][O.sub.3] (0.0

Several studies are employed to explain the structure, as well as the magnetic properties of the different Bi[Mn.sub.2][O.sub.5] multiferroic films are discussed. The application of swift heavy iron is shown to lead to the generation of ferrimagnetism in the films.

The magnetic, dielectric and electronic structural properties of Ti doped Bi[Mn.sub.2][O.sub.5] multiferroic materials are studied. The Ti L-edge spectra have shown the substitution of [Ti.sup.4+] ions in all samples and the x-ray diffraction as well as the x-ray absorption spectroscopy data and increase in net magnetic moment have indicated the replacement of [Mn.sup.4+] by [Ti.sup.4+].

The influence of Ti[O.sub.2] and ZnO oxides is examined on the conductivity and dielectric properties of unconventional and technologically important 40CuO-40[Bi.sub.2][O.sub.3]-20X (X = Ti[O.sub.2] and ZnO) glasses. Results reveal that the activation energy and dc conductivity of Ti[O.sub.2] containing glass are respectively higher and lower when compared to that of the ZnO containing glass.

The electronic, magnetic and thermal properties of polycrystalline Pr0.65Ca(sub 0.35-x)Sr(sub x)MnO3 (x=0-0.35) perovskites were explored. Huge enhancement of magnetoresistance in Pr0.65Ca(sub 0.35-x)Sr(sub x)MnO3 perovskites was observed for x~0.1 at low magnetic fields (< equal to 0.5 T) near the MI transition temperature.

The partial substitution of Cu by K in multicomponent glassy precursor for high Tc superconductor namely Bi(sub 2-x)Pb(sub x)Sr2Ca2Cu3O(sub delta) (x=0.1-0.3) is found to destroy superconductivity of the corresponding annealed phase. A comparison of the properties of the two glassy systems depicting distinguishing behavior is made.

Presents an examination of the alternating current conductivity of semiconducting oxide glasses. Experiment conducted; Results; Discussion.

We report the near edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) studies at the Mn L3,2 edge of pulsed laser deposited pristine thin films of multiferroic BiMn2O5. These investigations are furthermore testified for BiMn2O5 thin films irradiated through 200 MeV Ag15+ ions with fluence value 5×1011 ions/cm2. Though the pristine film is primarily antiferromagnetic in nature, irradiation induces ferrimagnetism in it. Element specific characterizations, NEXAFS and XMCD demonstrate the evolution of Mn2+ state piloting to magnetic signal associated with it. [ABSTRACT FROM AUTHOR]