Systematic induction of superconductivity in the Cu (Y1−xCax)Ba2Cu2O6+δ (\delta \approx 0.3 ) system by Ca substitution

Authors

V. Awana
M. Ansari
Rashmi NigamFollow
Anurag Gupta
S. Samanta
R. SaxenaFollow
H. Kishan
V. Ganesan
Anant Narlikar
M. Arai
Maarit Karppinen
Hisao Yamauchi
Devendra Buddhikot
S. Malik

RIS ID

41550

Publication Details

Awana, V. P., Ansari, M. A., Nigam, R., Gupta, A., Samanta, S. B., Saxena, R. B., Kishan, H., Ganesan, V., Narlikar, A. V., Arai, M., Karppinen, M., Yamauchi, H., Buddhikot, D. & Malik, S. K. (2005). Systematic induction of superconductivity in the Cu (Y_1−xCa_x)Ba₂Cu₂O_6+δ () system by Ca substitution . Superconductor Science and Technology, 18 (5), 716-720.

Abstract

Series of samples of the composition Cu (Y_1−xCa_x)Ba₂Cu₃O_6+δ () have been prepared by a solid-state synthesis route. Precise oxygen content was determined for all the samples by iodometric titration. The c lattice parameter increases with increasing x, indicating successful substitution of Y³⁺ by the bigger Ca²⁺ ion. Resistivity (R) versus temperature (T) measurements show that the pristine sample (x = 0.0) is semiconducting down to 5 K. Induction of superconductivity is seen with increasing x. The x = 0.10 sample exhibits the onset of superconducting transition (T_c^onset) at 42 K without attaining a zero resistance superconducting transition temperature (T_c^{R = 0}) state above 5 K. For the x = 0.15 and 0.20 samples T_c^{R = 0} is observed at 25 and 35 K with T_c^onset at 52 and 61 K, respectively. DC magnetic susceptibility measurements corroborated the findings from the resistivity measurements. Thermoelectric power (S) measurements in the temperature range of 5–300 K exhibit T_c^{S = 0} at 25 and 35 K respectively for x = 0.15 and 0.20 samples. The room-temperature S value decreases with increasing x, indicating an enhanced number of mobile holes. Magneto-transport measurements in applied magnetic fields of 3 and 6 T show a broadening of the superconducting transition. These results will be useful in constructing a more complete phase diagram of the Cu (Y_1−xCa_x)Ba₂Cu₃O_6+δ system in terms of x and δ.