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The study explains the superconducting properties of films that are deposited from micro-, nanocrystalline and optimally BaZr[O.sub.3] (BZO)-doped Y[Ba.sub.2][Cu.sub.3][O.sub.6X] (YBCO) targets. The doping is found to highly improve the properties of these films.

Investigating the transition in laser ablated films by increasing the barium concentration or by suppressing the potential Nd/Ba substitution by doping with calcium is discussed. It shows that the Ca-doped NBCO films have exceptionally smooth surfaces, but suggests their properties have a comparatively much weaker dependence on growth conditions.

We report the low-temperature anomalous magnetic behavior of ferrimagnetic spinels cobalt orthotitanate (Co2TiO4), which exhibits magnetic compensation behavior across 31.74 K, and cobalt orthostannate (Co2SnO4) exhibiting two sequential magnetic transitions, namely (i) ferrimagnetic to paramagnetic transition with Néel temperature TN∼41K and reentrant spin-glass behavior with glass transition temperature TSG∼39 K. The Arrott plot (H/M versus M²) criterion has been used to extricate the order of sequential magnetic transitions occurring below TN. Negative slopes of the Arrott plots below 32 K, metamagnetic-like character of the M-H isotherms, anomalies in the specific-heat (CP T-1 versus T) below 15 K, and a zero-crossover of isothermal magnetic-entropychange (ΔS) signify the presence of pseudo first-order discontinuous magnetic phase transition in the low-temperature regime 5K≤T≤32 K. The dc- and ac-susceptibilities of both Co2TiO4 and Co2SnO4 are interpreted in terms of frozen-spin-clusters, which are responsible for very large magnitudes of the coercivity HC∼20 kOe and bipolar-exchange bias HEB∼=-20 kOe observed below 10 K. [ABSTRACT FROM AUTHOR]

We report the growth of high indium content InGaN:Yb nanorods grown on c-plane sapphire (0001) substrates using plasma assisted molecular beam epitaxy. The in situ reflection high energy electron diffraction patterns recorded during and after the growth revealed crystalline nature of the nanorods. The nanorods were examined using electron microscopy and atomic force microscopy. The photoluminescence studies of the nanorods showed the visible emissions. The In composition was calculated from x-ray diffraction, x-ray photoelectron spectroscopy, and the photoluminescence spectroscopy. The In-concentration was obtained from photoluminescence using modified Vegard's law and found to be around 37% for InGaN and 38% for Yb (5±1%)-doped InGaN with a bowing parameter b=1.01 eV. The Yb-doped InGaN showed significant enhancement in photoluminescence properties compared to the undoped InGaN. The Yb-doped InGaN nanorods demonstrated the shifting of the photoluminescence band at room temperature, reducing luminescence amplitude temperature dependent fluctuation, and significant narrowing of excitonic emission band as compared to the undoped InGaN. The magnetic properties measured by superconducting quantum interference devices reveals room temperature ferromagnetism, which can be explained by the double exchange mechanism and magnetostriction. [ABSTRACT FROM AUTHOR]

We report the crystal structure, dielectric, magnetic, and magneto-electric properties of (1-x) BiFeO3-xYMnO3 (0.00 ≤ x ≤ 0.2) multiferroic nanoceramics prepared by auto-combustion technique. YMnO3 substitution is found to induce a structural phase transition from R3c to R3c+Pbnm after x ≈ 0.1 using Rietveld refinement technique. Field emission scanning electron micrographs show decrease in grain size with increase in YMnO3 content. The dielectric permittivity and loss tangent are found to be increased with composition x. The anomalies noticed from the temperature dependent dielectric analysis reveal the signature of magneto-electric coupling in the system. A decrease in magnetic ordering temperature as a function of composition is found from dielectric study. At room temperature, the dielectric permittivity of all the YMnO3 modified samples decrease with increasing magnetic field. The maximum value of magneto-electric coupling coefficient ([variant_greek_epsilon](H)-[variant_greek_epsilon](0))/[variant_greek_epsilon](0) is found to be ∼ -5.5% at H = 2 T for x = 0.2. The behaviour of the magnetic hysteresis loop observed at room temperature suggests the suppression of space modulated spin structure. [ABSTRACT FROM AUTHOR]

A robust magnetoelectric (ME) response is essential in multiferroic thin films for potential nonvolatile ME memory elements. We report strong ME effects in bilayers and superlattices of Ba0.7Sr0.3TiO3/La0.7Sr0.3MnO3 composite multiferroics. The low-frequency ME coefficient ranges from 35 to 300 mV/cm Oe, depending on thickness, superlattice periodicity, and bias magnetic field and ac magnetic field orientations. Data on ME coupling are fitted well with a modified free-body model to obtain information on magneto-mechanical coupling in the composites. The strong ME coupling in spite of anticipated substrate clamping is a step forward towards the realization of multistate memories and read-write elements. [ABSTRACT FROM AUTHOR]

Polarized resonant Raman scattering studies have been performed on monolayer, bilayer, and suspended bilayer graphene. The intensity of the G band is found to be unchanged with polarization in monolayer and bilayer graphene, whereas it shows polarization dependence in suspended bilayer graphene. The 2D mode shows strong polarization depended behavior for all the samples, irrespective of layer thickness. It is found that the intensity of the 2D peak is at a maximum when the incident photon is parallel to the scattered photon and at a minimum when these are perpendicular to each other. This effect has been explained on the basis of anisotropic photon scattering through the nodes at the K-point of the Brillouin zone in graphene during optical absorption. [ABSTRACT FROM AUTHOR]

Superlattices (SLs) with different periodicity of ferromagnetic La0.7Sr0.3MnO3 (LSMO) and ferroelectric Ba0.7Sr0.3TiO3 as constitutive layers were fabricated on conducting LaNiO3 coated (001) oriented MgO substrates using pulsed laser deposition. The crystallinity, ferroelectric, and magnetic properties of the SLs were studied over a wide range of temperatures and frequencies. The structure exhibited ferromagnetic behavior at 300 K and ferroelectric behavior over a range of temperatures between 100 and 300 K. A frequency-dependent change in dielectric constant and tangent loss were observed above the ferromagnetic-paramagnetic temperature. The frequency-dependent dielectric anomalies are attributed to the change in metallic and magnetic nature of LSMO and also the interfacial effect of two different phases that are connected alternatively in series. The effect of ferromagnetic LSMO layers on ferroelectric properties of the SLs indicated strong influence of the interfaces. The asymmetric behavior of ferroelectric loop and the capacitance-voltage relationship suggest development of a built field in the SLs due to high strain across the interfaces. [ABSTRACT FROM AUTHOR]

Highly oriented Pb([Fe.sub.1/2][Ta.sub.1/2])[O.sub.3] (PFT) film is prepared on conducting [La.sub.0.67][Sr.sub.0.33]Co[O.sub.3] coated (100) MgO substrate by using pulsed laser deposition method. A large shift in dielectric maximum temperature is observed when compared to bulk counterpart that is due to misfit strain across substrate-bottom electrode-film interface and in plane compressive strain in the film.

In this article, we report a comparative analysis of various spectroscopic studies including low-temperature ( [ABSTRACT FROM AUTHOR]

We report the localized charge carrier transport of two-phase composite ZnNiO/NiO (0 ≤ x ≤ 1) using the temperature dependence of ac-resistivity ρ( T) across the Néel temperature T (= 523 K) of nickel oxide. Our results provide strong evidence to the variable range hopping of charge carriers between the localized states through a mechanism involving spin-dependent activation energies. The temperature variation of carrier hopping energy ε( T) and nearest-neighbor exchange-coupling parameter J( T) evaluated from the small poleron model exhibits a well-defined anomaly across T. For all the composite systems, the average exchange-coupling parameter ( J) nearly equals to 70 meV which is slightly greater than the 60-meV exciton binding energy of pure zinc oxide. The magnitudes of ε (∼0.17 eV) and J (∼11 meV) of pure NiO synthesized under oxygen-rich conditions are consistent with the previously reported theoretical estimation based on Green's function analysis. A systematic correlation between the oxygen stoichiometry and, ε( T) and J( T) is discussed. [ABSTRACT FROM AUTHOR]

The InGaN thin films with indium content of x = 14-18 at.% were successfully grown by using molecular beam epitaxy (MBE) at high growth temperatures from 650°C to 800°C. In situ reflection high-energy electron diffraction (RHEED) of the InGaN films confirmed the Stranski-Krastanov growth mode. X-ray diffraction (XRD) of the films confirmed their highly crystalline nature having c-axis orientation with a small fraction of secondary InN phase admixture. High-resolution cross-sectional scanning electron microscopy images showed two-dimensional epilayers growth with thickness of about ∼260 nm. The high growth temperature of InGaN epilayers is found to be favorable to facilitate more GaN phase than InN phase. All the fundamental electronic states of In, Ga, and N were identified by x-ray photoelectron spectroscopy (XPS) and the indium composition has been calculated from the obtained XPS spectra with CASAXPS software. The composition calculations from XRD, XPS and photoluminescence closely match each other. The biaxial strain has been calculated and found to be increasing with the In content. Growing InGaN at high temperatures resulted in the reduction in stress/strain which affects the radiative electron-hole pair recombination. The InGaN film with lesser strain showed a brighter and stronger green emission than films with the larger built-in strain. A weak S-shaped near band edge emission profile confirms the relatively homogeneous distribution of indium. [ABSTRACT FROM AUTHOR]