A comprehensive review on vibration based micro power generators using electromagnetic and piezoelectric transducer mechanisms

Applications of the non-line-of-sight vapor deposition techniques, such as chemical vapor deposition (CVD) and atomic layer deposition (ALD), offer unique opportunities to produce well-defined high surface area current collectors, thin films or various nanostructures of active (ion-storage) materials, protective coatings, solid electrolytes and improved separators. These features hold significant promise for solving emerging issues in advanced LiBs and supercapacitors. This paper reviews recent developments and applications of CVD and ALD for these energy storage devices, providing selected examples and outlining critical challenges for further exploration.

Chemical vapor deposition and atomic layer deposition for advanced lithium ion batteries and supercapacitors

The symmetry of Cooper pairs in iron-based superconductors is an issue under continued investigation. A scanning tunnelling study of Fe(Te,Se) reveals a robust zero-energy bound state, providing evidence for a non-trivial pairing symmetry.

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Observation of a robust zero-energy bound state in iron-based superconductor Fe(Te,Se)

Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1089&context=ameslab_manuscripts

Nematicity, magnetism and superconductivity in FeSe

Mn4+-doped Y2MgTiO6 phosphors are synthesized by the traditional solid-state method. Powder X-ray diffraction, scanning electron microscope, and energy-dispersive X-ray spectrometer are employed to...

Optical Thermometry Based on Vibration Sidebands in Y2MgTiO6:Mn4+ Double Perovskite

Antisite disorder is observed to have significant impact on the magnetic properties of the double perovskite Y2CoMnO6 which has been recently identified as a multiferroic. A paramagnetic-ferromagnetic phase transition occurs in this material at Tc ≈ 75 K. At 2 K, it displays a strong ferromagnetic hysteresis with a significant coercive field of Hc ≈ 15 kOe. Sharp steps are observed in the hysteresis curves recorded below 8 K. In the temperature range 2 K ≤ T ≤ 5 K, the hysteresis loops are anomalous as the virgin curve lies outside the main loop. The field-cooling conditions as well as the rate of field-sweep are found to influence the steps. Quantitative analysis of the neutron diffraction data shows that at room temperature, Y2CoMnO6 consists of 62% of monoclinic P21/n with nearly 70% antisite disorder and 38% Pnma. The bond valence sums indicate the presence of other valence states for Co and Mn which arise from disorder. We explain the origin of steps by using a model for pinning of magnetization at the antiphase boundaries created by antisite disorder. The steps in magnetization closely resemble the martensitic transformations found in intermetallics and display first-order characteristics as revealed in the Arrott's plots.

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Magnetization-steps in Y2CoMnO6 double perovskite: The role of antisite disorder

The parent compound of iron chalcogenide superconductors, Fe1+yTe, with a range of excess Fe concentrations exhibits intriguing structural and magnetic properties. Here, the interplay of magnetic and structural properties of Fe1.12Te single crystals have been probed by low-temperature synchrotron X-ray powder diffraction, magnetization, and specific heat measurements. Thermodynamic measurements reveal two distinct phase transitions, considered unique to samples possessing excess Fe content in the range of 0.11 <= y <= 0.13. On cooling, an antiferromagnetic transition, T-N approximate to 57K is observed. A closer examination of powder diffraction data suggests that the transition at TN is not purely magnetic, but accompanied by the commencement of a structural phase transition from tetragonal to orthorhombic symmetry. This is followed by a second prominent first-order structural transition at T-S with T-S < T-N, where an onset of monoclinic distortion is observed. The results point to a strong magneto-structural coupling in this material. (C) 2014 AIP Publishing LLC.

Structural and thermodynamic properties of Fe1.12Te with multiple phase transitions

Specific heat, resistivity, magnetic susceptibility, linear thermal expansion (LTE), and high-resolution synchrotron x-ray powder diffraction investigations of single crystals Fe${}_{1+y}$Te (0.06 $\ensuremath{\le}y\ensuremath{\le}$ 0.15) reveal a splitting of a single, first-order transition for $y\ensuremath{\le}$ 0.11 into two transitions for $y\ensuremath{\ge}$ 0.13. Most strikingly, all measurements on identical samples Fe${}_{1.13}$Te consistently indicate that, upon cooling, the magnetic transition at ${T}_{N}$ precedes the first-order structural transition at a lower temperature ${T}_{s}$. The structural transition in turn coincides with a change in the character of the magnetic structure. The LTE measurements along the crystallographic $c$ axis display a small distortion close to ${T}_{N}$ due to a lattice striction as a consequence of magnetic ordering, and a much larger change at ${T}_{s}$. The lattice symmetry changes, however, only below ${T}_{s}$ as indicated by powder x-ray diffraction. This behavior is in stark contrast to the sequence in which the phase transitions occur in Fe pnictides.

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First-order structural transition in the magnetically ordered phase of Fe1.13Te

We have investigated the influence of Fe excess on the electrical transport and magnetism of Fe1+yTe0.5Se0.5 (y=0.04 and 0.09) single crystals. Both compositions exhibit resistively determined superconducting transitions (T-c) with an onset temperature of about 15 K. From the width of the superconducting transition and the magnitude of the lower critical field H-c1, it is inferred that excess of Fe suppresses superconductivity. The linear and nonlinear responses of the ac susceptibility show that the superconducting state for these compositions is inhomogeneous. A possible origin of this phase separation is a magnetic coupling between Fe excess occupying interstitial sites in the chalcogen planes and those in the Fe-square lattice. The temperature derivative of the resistivity d(rho)/d(T) in the temperature range T-c < T < T-a with T-a being the temperature of a magnetic anomaly, changes from positive to negative with increasing Fe. A log 1/T divergence of the resistivity above T-c in the sample with higher amount of Fe suggests a disorder-driven electronic localization.

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Disorder-driven electronic localization and phase separation in superconducting Fe1+yTe0.5Se0.5 single crystals

The evolution of magnetic polarons in Sr doped LaCoO3 (La1-xSrxCoO3) single crystal and polycrystalline samples are investigated by employing dc and ac magnetic measurement and small angle neutron ...

https://link.aps.org/pdf/10.1103/PhysRevResearch.2.043344

Dona Cherian

Papers

Magnetization-steps in Y2CoMnO6 double perovskite: The role of antisite disorder

Structural and thermodynamic properties of Fe1.12Te with multiple phase transitions

First-order structural transition in the magnetically ordered phase of Fe1.13Te

Disorder-driven electronic localization and phase separation in superconducting Fe1+yTe0.5Se0.5 single crystals

Magnetic polarons and spin-glass behavior in insulating La 1 − x Sr x Co O 3 ( x = 0.125 and 0.15)