Yange Zhang

Ultrasonic study on magnetic-field-induced stripe order in La1.88Sr0.12-xBaxCuO4

The ultrasonic sound velocities and attenuations of La1.88Sr0.12-xBaxCuO4 (0 <= x <= 0.12) under magnetic fields of up to 14 T show two important features of charge stripe order in the system. The first is that the ultrasonic characteristics indicate the existence of local stripe order associated with low temperature tetragonal structure domains for samples with x <= 0.04. The second is that the local stripe order can be enhanced by magnetic fields. The results indicate a strong interaction between charge stripes and crystal lattice in the system.

Effect of Temperature on La1.85Sr0.15CuO4 Single Crystal Growth by Floating Zone Method

Superconducting single crystals of La1.85Sr0.15CuO4 have been grown at various temperatures without single crystal seeds by the traveling-solvent floating-zone method. In order to avoid the formation of bubbles during the crystal growth process, a flowing atmosphere of 2 atm oxygen or 1 atm air was applied in different temperature range. It was found that the crystal quality could be improved by raising the growth temperature in a certain range, and the orientation changed from (110) to (100) at higher temperature. X-ray diffraction results showed that the full-width at half-maximum of the best as-prepared crystal was 0.086°. The crystals grown in 2 atm oxygen showed a superconducting transition temperature (Tc) of 37.3 K, while the crystals grown in floating air showed a Tc of about 35 K and it could be improved to 36.5 K by annealing in flowing oxygen.