[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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Dye-Sensitized Solar Cells

BiFeO3 is perhaps the only material that is both magnetic and a strong ferroelectric at room temperature. As a result, it has had an impact on the field of multiferroics that is comparable to that of yttrium barium copper oxide (YBCO) on superconductors, with hundreds of publications devoted to it in the past few years. In this Review, we try to summarize both the basic physics and unresolved aspects of BiFeO3 (which are still being discovered with several new phase transitions reported in the past few months) and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.

Physics and Applications of Bismuth Ferrite

Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, have recently stimulated a sharply increasing number of research activities for their scientific interest and significant technological promise in the novel multifunctional devices. Natural multiferroic single-phase compounds are rare, and their magnetoelectric responses are either relatively weak or occurs at temperatures too low for practical applications. In contrast, multiferroic composites, which incorporate both ferroelectric and ferri-/ferromagnetic phases, typically yield giant magnetoelectric coupling response above room temperature, which makes them ready for technological applications. This review of mostly recent activities begins with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972. In such composites the magnetoelectric effect is generated as a product property of a magnetostrictive and a piezoelectric substance. A...

Multiferroic magnetoelectric composites: Historical perspective, status, and future directions

R J Baxter 1982 London: Academic xii + 486 pp price £43.60 Over the past few years there has been a growing belief that all the twodimensional lattice statistical models will eventually be solved and that it will be Professor Baxter who solves them. Baxter has inherited the mantle of Onsager who started the process by solving exactly the two-dimensional Ising model in 1944.

Exactly Solved Models in Statistical Mechanics

The ordering of the classical Ising model on the Archimedean lattice that is topologically equivalent to the Shastry-Sutherland one is studied in order to understand the fascinating magnetic properties experimentally observed in rare-earth tetraborides such as TmB4. The long-range Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction which is expected to be predominant in these systems is taken into account, and the magnetization plateaus and rich ordering behaviors depending on the Fermi wave vector are investigated in details by Monte Carlo simulation. The experimental 1/2 magnetization step can be qualitatively reproduced and its stability against the change of is confirmed, suggesting that the coupling between conduction electrons and localized moments may play an important role in modulating the magnetization behaviors in these systems.

http://iopscience.iop.org/article/10.1209/0295-5075/105/17009/pdf

The main 1/2 magnetization plateau in Shastry-Sutherland magnets: Effect of the long-range Ruderman-Kittel-Kasuya-Yosida interaction

Ultrathin high-k HfAlOx films on silicon wafers are prepared by pulsed-laser deposition in oxygen-defective ambient. The precipitation of HfOx clusters from HfAlOx matrix is revealed by x-ray photoelectron spectroscopy. It is argued that the HfOx clusters react with silicon to form Hf-silicide interfacial layer at a temperature as low as 600 degrees C, which evolves into Hf-silicate in the subsequent postannealing at 700 degrees C for 30 s in oxygen ambient. The optimized fabrication conditions developed to avoid the formation of interfacial layer is employed to prepare high-quality HfAlOx films of excellent electrical characteristics, such as a dielectric constant of 17.7, a small equivalent oxide thickness of 0.66 nm, a flatband voltage of 0.45 V, and a low leakage current density of 53.8 mA/cm(2) at 1 V gate voltage.

Phase separation and interfacial reaction of high-k HfAlOx films prepared by pulsed-laser deposition in oxygen-deficient ambient

Polycrystalline ${\mathrm{La}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3\ensuremath{-}\ensuremath{\delta}}$ thin films deposited on quartz wafers at 680 \ifmmode^\circ\else\textdegree\fi{}C and various oxygen pressures P by pulsed laser deposition are prepared. The effects of oxygen nonstoichiometry on the microstructural, electrotransport and low-field magnetotransport property of the thin films are investigated in details. A structural distortion from the stoichiometric lattice is identified for the samples deposited at $Pl0.1\mathrm{mbar}.$ It is verified that the thin-film conductivity over the Curie point follows variable-range hopping. The carrier density at the Fermi surface falls and the metal-insulating transition shifts toward low temperature with decreasing P, with a jump at $P=0.1\mathrm{mbar}.$ Enhanced low-field magnetoresistance at low temperature is achieved for $Pg0.1\mathrm{mbar}.$ Oxygen overdeficiency at $Pl~0.1\mathrm{mbar}$ essentially prohibits the spin reordering. The temperature dependence of the electro- and magnetotransport properties is explained by the two-channel model where the insulating channels and metallic ones coexist in parallel.

Effect of oxygen nonstoichiometry on electrotransport and low-field magnetotransport property of polycrystalline La 0.5 Sr 0.5 MnO 3 − δ thin films

We apply the Wigner-Yanase skew information approach to analyze two typical models that exhibit a topological quantum phase transition. Based on the exact solutions of the ground states, the Wigner-Yanase skew information between two nearest sites for each of the two models is obtained. For the one-dimensional Kitaev chain model, the first-order derivative of the Wigner-Yanase skew information is non-analytical around the critical point. The scaling behavior and the universality are verified numerically. In particular, the skew information can also detect the factorization transition in such a model. For the two-dimensional Kitaev honeycomb model, the first-order derivative of the Wigner-Yanase skew information shows some singularities at the critical points where the system transits from the gapless phase to the gapped one. Our results suggest that the Wigner-Yanase skew information can serve as a good indicator of the topological phase transitions in these models and shed considerable light on the relationships between topological quantum phase transition and information theory.

https://iopscience.iop.org/article/10.1209/0295-5075/108/46003/pdf

Signature of topological quantum phase transitions via Wigner-Yanase skew information

The grain-boundary structure and the temperature dependence of resistivity were investigated for (1-x)LCMO + xYSZ, where LCMO and YSZ represent La2/3Ca1/3MnO3 and yttria-stabilized zirconia, respectively. It is shown that the YSZ doped samples for x 2%. The metal-insulator transition temperature (Tp) decreases for x 2% as x is increased. LFMR increases with x for x 2%. The experimental observations are discussed on the basis of scanning electron microscopy (SEM) analysis, which reveals YSZ appearing at the grain boundaries of LCMO for x 2%.

J.-M. Liu

Papers

The main 1/2 magnetization plateau in Shastry-Sutherland magnets: Effect of the long-range Ruderman-Kittel-Kasuya-Yosida interaction

Phase separation and interfacial reaction of high-k HfAlOx films prepared by pulsed-laser deposition in oxygen-deficient ambient

Effect of oxygen nonstoichiometry on electrotransport and low-field magnetotransport property of polycrystalline La 0.5 Sr 0.5 MnO 3 − δ thin films

Signature of topological quantum phase transitions via Wigner-Yanase skew information

Grain boundaries and low-field transport properties in colossal magnetoresistance materials