相关论文: Structural Phase Transitions and Sodium Ordering i…
We have synthesized and characterized four different stable phases of Na ordered Na$_{x}$CoO$_{2}$, for $0.65<x<0.8$. Above 100 K they display similar Curie-Weiss susceptibilities as well as ferromagnetic $q=0$ spin fluctuations in the…
We have grown single crystals of Na$_x$Ca$_y$CoO$_2$ and determined their superstructures as a function of composition using neutron and x-ray diffraction. Inclusion of Ca$^{2+}$ stabilises a single superstructure across a wide range of…
New electronic phases have been identified and placed in the (T,H) phase diagram of metallic NaxCoO2. At low Na-content (x = 0.36), the magnetic susceptibility diverges with a power law T^(-n), n<1, and shows (T,H) scaling, indicating the…
Using a combination of low-temperature nanocalorimetry and x-ray diffraction we identify three temperature regimes characterized by distinct Na ordering patterns (low temperature up to 290 K, intermediate 290-340 K, and high above 340 K).…
The structural and magnetic properties of Ge0.5Mn0.5Co2O4 (GMCO) have been investigated in detail utilizing neutron powder diffraction (NPD), x-ray diffraction (XRD), DC magnetometry, and heat capacity analysis and compared with GeCo2O4.…
We investigate the electronic and structural changes at the nanoscale in vanadium dioxide (VO2) in the vicinity of its thermally driven phase transition. Both electronic and structural changes exhibit phase coexistence leading to…
In this paper we report the growth and superconductivity of $Na_xTaS_2$ crystals. The structural data deduced from X-ray diffraction pattern shows that the sample has the same structure as $2H-TaS_2$. A series of crystals with different…
Powder Na$_{x}$CoO$_{2}$ ($0.70\leq x\leq 0.84$) samples were synthesized and characterized carefully by X-ray diffraction analysis, inductive-coupled plasma atomic emission spectroscopy, and redox titration. It was proved that…
The structural, dielectric and ferroelectric properties of lead-free (Na0.5-xKxBi0.5-xLax)TiO3 powders synthesized by sol-gel self-combustion method were investigated. Rietveld refinement of Synchrotron x-ray diffraction data confirms pure…
The impact of oxygen deficiency on physical properties of Na2/3CoO2-x has been investigated. From the combined thermogravimetric, magnetic susceptibility and synchrotron X-ray Laue diffraction studies, it is demonstrated that Na2/3CoO2…
We report a complete analysis of the formal oxidation state of Co in NaxCoO2, in the interval 0.31<x<0.67. Iodometric titration and thermoelectric power confirm that a direct relationship between the Na content and the amount of Co 3 +…
The nature of the phase separation in KxFe2-ySe2 single crystals is not well understood. Here, temperature dependent SEM images provide compelling evidence that phase separation corresponds to a nucleation and growth process rather than a…
We measured the pressure dependence of in-plane resistivity $\rho_{ab}$ in the recently-discovered iron-based superconductor Ca$_{10}$(Ir$_{4}$As$_{8}$)(Fe$_{2-x}$Ir$_{x}$As$_{2}$)$_{5}$, which shows a unique structural phase transition in…
Phase separation of metallic and antiferromagnetic (AFM) insulating phases in alkaline iron selenides (AxFe2-ySe2) continues to attract intense interest because the relationship between two peculiar features probably is a key to clarifying…
Aliovalent rare earth substitution into the alkaline earth site of CaFe2As2 single-crystals is used to fine-tune structural, magnetic and electronic properties of this iron-based superconducting system. Neutron and single crystal x-ray…
We have investigated the preparation and bulk magnetic properties of NaxCoO2 in the range 0.5<x<0.95, including those for single crystals grown by the floating-zone method in an image furnace. To characterize the samples and ascertain their…
Electronic phase diagram of LixCoO2 has been re-examined using potentiostatically de-intercalated single crystal samples. Stable phases of x ~ 0.87, 0.72, 0.53, 0.50, 0.43, and 0.33 were found and isolated for physical property studies.…
Comparison is made of the electronic structure of the little-studied layered transition metal oxide LiNbO$_2$ with that of Na$_x$CoO$_2$, which has attracted tremendous interest since superconductivity was discovered in its hydrate.…
Superconducting single crystal samples of Na_xCoO_2 + yH_2O have been produced using an electrochemical technique which dispenses with the usual bromine chemical de-intercalation step and permits much more precise control of the Na content.…
We report the synthesis and superconducting properties of a metastable form of the known superconductor NaxCoO2*yH2O (x ~ 1/3, y ~ 4x). Instead of using the conventional bromine-acetonitrile mixture for sodium deintercalation, we use an…