Anisotropic optical spectra of PrBa2Cu4O8: possible Tomonaga-Luttinger liquid response of the quasi-one-dimensional metallic CuO double chains

The optical spectra of PrBa2Cu4O8 show large in-plane anisotropy. For the a polarization (E perpendicular chain), the spectrum is characterized by a gap of 1.4 eV, indicating the charge-transfer insulating nature of the CuO2 planes. For the metallic chain direction (E // b), the spectrum deviates from a simple Drude response; reflectivity R(b)(omega) shows a sharp edge at approximately 1 eV but it also shows a dip at approximately 15 meV, which splits the conductivity spectrum into two parts--a zero-energy mode with small weight and a pronounced 40 meV mode. These features are discussed in terms of a Tomonaga-Luttinger liquid in a doped 1D Mott insulator and compared with 1D Bechgaard salts.     

Pressure and temperature dependence of the structure of liquid Sn up to 5.3 GPa and 1373 K

Pressure and temperature dependence of the structure of liquid Sn has been measured up to 5.3?GPa and 1373?K using multi-angle energy-dispersive X-ray diffraction in Paris–Edinburgh cell. Under nearly isobar condition at ～1?GPa, liquid Sn displays a normal behavior with gradual structural changes with temperature up to 1373?K. Under isothermal compressions at 850 and 1373?K, however, the structure factors of liquid Sn both show a turn-over at ～3?GPa in the height of the first diffraction peak. According to the hard sphere cluster model, the structure of liquid Sn may be viewed as two different types of clusters. Below ～3?GPa, it is shown that the packing fraction of the dominant cluster (occupying ～0.94 fraction) changes with compression, while above ～3?GPa, the packing fractions and the hard sphere diameters of both clusters start to influence the structure, causing significant changes with increasing pressure. Our results suggest that the compression behavior of liquid Sn changes from localized densification only in one cluster below ～3?GPa to homogeneous structural changes in both clusters above ～3?GPa.     

Fabrication of zinc ferrite nanocrystals by sonochemical emulsification and evaporation: observation of magnetization and its relaxation at low temperature

A new ultrasound assisted emulsion (consisting of rapeseed oil and aqueous solution of Zn(2+) and Fe(2+) acetates) and evaporation protocol has been developed for the synthesis of zinc ferrite (ZnFe(2)O(4)) nanoparticles with narrow size distribution. The as-synthesized sample consisted of crystalline zinc ferrite particles with an average diameter of approximately 4 nm, whereas the average size of the heat-treated ferrite particles increases to approximately 12 nm. To remove the small amount of oil present on the surface of the as-synthesized ferrite sample, heat treatment was carried out at 350 degrees C for 3 h. The as-synthesized and heat-treated ferrites were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), TGA/DTA, transmission electron microscopy (TEM), and energy dispersion X-ray spectroscopy (EDS) techniques. Magnetic measurements show that the nanocrystalline ZnFe(2)O(4), prepared through this technique, is either at par with those obtained in other cases or even more improved. Both the as-synthesized and heat-treated samples reveal relaxation of magnetization. Our study also shows that one can tailor the magnetization and relaxation pattern by suitably controlling the particle size of the nanocrystalline ZnFe(2)O(4). The key features of this method are avoiding (a) the cumbersome conditions that exist in the conventional methods, (b) the usage of necessary additive components (stabilizers or surfactants, precipitants), and (c) calcination requirements. In addition, rapeseed oil has replaced organic nonpolar solvents used in earlier studies. As a whole, this simple straightforward sonochemical approach results in a better pure phase system of nanoferrite with improved magnetic properties.     

Spin models constructed from Hadamard matrices

A spin model (for link invariants) is a square matrix W which satisfies certain axioms. For a spin model W, it is known that W ^T W ^?1 is a permutation matrix, and its order is called the index of W. Jaeger and Nomura found spin models of index?2, by modifying the construction of symmetric spin models from Hadamard matrices. The aim of this paper is to give a construction of spin models of an arbitrary even index from any Hadamard matrix. In particular, we show that our spin models of indices a power of 2 are new.