Keiki Takeda

Systematic Study of Lattice Specific Heat of Filled Skutterudites

The lattice specific heat C lat of La-based filled skutterudites La T 4 X 12 ( T = Fe, Ru and Os; X = P, As, and Sb) has been systematically studied, and both the Debye temperature Θ D and the Einstein temperature Θ E of La T 4 X 12 were carefully estimated. We confirmed that a correlation exists between Θ D and the reciprocal of the square root of average atomic mass for La T 4 P 12 , La T 4 As 12 , and La T 4 Sb 12 . The Θ D of filled skutterudites was found to depend mainly on the nature of the species X forming the cage. The temperature dependence of C lat / T 3 for La T 4 X 12 exhibited a large broad maximum at low temperatures (10–30 K), which suggests a nearly dispersionless low-energy optical mode characterized by Einstein specific heat. Since no such broad maximum exists for the unfilled skutterudite RhP 3 , the low-energy optical modes are associated with vibration involving La ions in the X 12 cage (the so-called “guest ion modes”). The Θ E of filled skutterudites was found to roughly correspon...

Pressure-Induced Superconductivity Emerging from Antiferromagnetic Phase in CeNiGe3

The antiferromagnet CeNiGe 3 exhibits superconductivity under pressure. The Neel temperature initially increases with increasing pressure up to 3 GPa and then becomes zero at a critical pressure ( ...

Pressure-Temperature Phase Diagram and Superconductivity in UIr

Pressure-induced superconductivity is found in UIr without inversion symmetry. The pressure–temperature phase diagram has been investigated by means of the electrical resistivity, ac-susceptibility and magnetization measurements under high pressure. The phase diagram consists of three magnetic phases FM1–3 and a superconducting phase. The huge enhancement of residual resistivity and the negative magnetoresistance are found in the intermediate pressure region. These behavior may be induced by the pressure-induced structural phase transition and the accompanied phase separation in this pressure range. The superconducting phase with narrow pressure range is embedded in the FM3 phase, adjacent to zero-temperature FM3-to-nonmagnetic transition. The temperature dependence of resistivity above T SC follows non-Fermi liquid form of T 1.6 . From these experimental facts, superconductivity is considered to be associated with the ferromagnetic fluctuation.

Superconductivity of the new skutterudite compound LaxRh4P12 prepared at high pressure

A new skutterudite compound LaxRh4P12 has been prepared at around 1100 °C and 4 GPa. This product was characterized by powder x-ray diffraction at ambient pressure. The x-ray diffraction profile of LaxRh4P12 is indexed to the filled skutterudite-type structure. The lattice constant of this sample is 8.0581(5) A. The x value estimated from x-ray diffraction and electron probe microanalysis data is about 0.6. Electrical and magnetic properties of this compound have been studied at low temperatures. LaxRh4P12 showed a superconducting transition at around 17 K. This compound has the highest Tc among metal phosphides. The thermoelectric power of the new compound is negative, S = −47 µV K−1, at room temperature. The new superconducting material LaxRh4P12 is an n-type conductor.

Pressure-induced unconventional superconductivity in the heavy-fermion antiferromagnet CeIn 3 : An In 115 -NQR study under pressure

We report on pressure-induced unconventional superconductivity (SC) in the heavy-fermion (HF) antiferromagnet

Valence Crossover of Ce Ions in CeCu2Si2 under High Pressure - Pressure Dependence of the Unit Cell Volume and the NQR Frequency

{\mathrm{CeIn}}_{3}

Structural, Optical, and Electrical Properties of One-Dimensional Bis(Dimethylglyoximato)nickel(II), Ni(dmg)2 at High Pressure

by means of nuclear-quadrupole-resonance (NQR) studies conducted under a high pressure. The temperature

Pressure-induced irreversible isosymmetric transition of TSb3 (T=Co, Rh and Ir)

(T)

High-pressure Synthesis and Structural, Electrical and Magnetic Properties of a New Filled Skutterudite TbFe4P12

and pressure

Compressibility and High-Pressure Electrical Resistivity of One-Dimensional Phthalocyanine Conductors: The Relationship with d-π Charge Transfer

(P)