Y. Koike

Anomalous x dependence of Tc and possibility of low-temperature structural phase transition in La2−xSrxCu0.99M0.01O4 (M Ni, Zn, Ga)

Abstract Effects of the 1% substitution of Ni, Zn and Ga for Cu on the x dependence of T c have been investigated in La 2−x Sr x CuO 4 . The T c increases by the Cu-site substitution in all compositions of x. The local minimum of T c as a function of x, appearing slightly near x = 0.115 for La 2−x Sr x CuO 4 , becomes conspicuous with decreasing T c . However, structural phase transition from the orthorhombic mid-temperature phase to the tetragonal low-temperature phase has not been detected from powder X-ray diffraction measurements at low temperatures down to 12 K. The local minimum of T c is attributable to the fluctuation of the undiscovered structural phase transition, which will occur at a low temperature below 12 K as long as samples are in the normal-conducting state. In the 1% Ga-substituted system for Cu, the local minimum clearly shifts from x = 0.115 to 0.125. This suggests that the undiscovered low-temperature structural phase transition is due to the optimum hole concentration of 0.115 per Cu atom, analogously to La 2−x Ba x CuO 4 .

Trial of intercalation of Br and Li into Bi2Sr2Can−1CunO2n+4 (n = 1, 2, 3)

Abstract Intercalation of Br and Li into Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 ( n = 1, 2, 3) has been tried. For heavily Br-intercalated samples of n = 2 and 3 with x ≈ 1 in Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 Br x , enlargement of the c-axis is detected, suggesting that intercalation compounds Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 Br with Br atoms between double BiO layers are synthesized. For Li-intercalated samples, on the other hand, clear evidence to show the formation of intercalation compounds is not obtained. For lightly Br- and Li- intercalated samples of n = 1, 2, 3, changes of the electrical resistivity, the Hall coefficient and T c by the intercalation are observed, which are attributable to charge transfer between intercalants and CuO 2 planes in the host materials Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 . That is, the intercalation of Br and Li is effective for hole and electron doping into CuO 2 planes, respectively. For n = 3, T c decreases by the light intercalation of both Br and Li, suggesting that Bi 2 Sr 2 Ca 2 Cu 3 O 10 has almost optimum hole concentration to attain the maximum of T c .

Superconductivity and low-temperature structural phase transition in La1.98-xCe0.02BaxCuO4

Abstract Effects of the partial substitution of Ce for La on the superconductivity and the low-temperature structural phase transition have been investigated in La2-xBaxCuO4. The local minimum of Tc as a function of Ba concentration x, appearing near x = 0.125 for La2-xBaxCuO4, clearly shifts to x = 0.145 for La1.98-xCe0.02BaxCuO4. The range of x, where a resistance minimum relating to the low-temperature structural phase transition appears, shifts to that of larger x values, too. These suggest that the low-temperature structural phase transition around x = 0.125 in La2-xBaxCuO4 is due to the optimum hole concentration of 0.125 per Cu atom rather than plausible atomic ordering of La and Ba.

Crystal growth, transport properties, and crystal structure of the single-crystal La2-xBaxCuO4 (x=0.11)

We have attempted the crystal growth by the traveling-solvent floating-zone (TSFZ) method of

Role of Lattice Coupling in Establishing Electronic and Magnetic Properties in Quasi-One-Dimensional Cuprates

{\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Ba}}_{x}{\mathrm{CuO}}_{4}(x\ensuremath{\sim}1/8),

Cu spin dynamics in the overdoped regime of La2-xSrxCu1-yZnyO4 probed by muon spin relaxation

where the superconductivity is strongly suppressed. Under flowing

Magnetic-field effects on the in-plane electrical resistivity in single-crystal La2-xBaxCuO4 and La1.6-xNd0.4SrxCuO4 around x = 1/8 : Implication for the field-induced stripe order

{\mathrm{O}}_{2}

Spin Gap and Hole Pairing of Sr14−xA x Cu24O41(A = Ca and La) Single Crystals Studied by the Electrical Resistivity and Thermal Conductivity

gas at high pressure (4 bars), we have succeeded in growing single crystals for

Effects of the Cu-site substitution on the anomalous x dependence of Tc in La2−xBaxCuO4

x=0.11

Similarity between Ni and Zn impurity effects on the superconductivity and Cu-spin correlation in La2-xSrxCu1-yNi yO4 high-Tc cuprates: A comparison based on the hole trapping by Ni

of 5 mm in diameter and 20 mm in length. Both in-plane and out-of-plane electrical resistivities of single-crystal