Properties of La1.8Sr0.2CuO4 superconductors

Abstract

Critical current, critical field, and carrier density measurements have been made on bulk samples of La_1.8Sr_0.2CuO₄ to assess the potential of such oxide superconductors for practical applications. The importance of preparing samples in a high oxygen pressure was documented. The upper critical field at T=0 was estimated to be 530 kOe. From magnetization hysteresis loops, critical current densities were determined between 0 and 60 kOe. At 60 kOe, the values were 2×10³ A/cm² at 4.2 K and 4×10² A/cm² at 18 K in samples that exhibited characteristics of weak flux pinning. The effective carrier density at 48 K was 1×10²¹ cm⁻³, approximately half of the expected upper limit. A set of microscopic superconducting parameters has been derived from transition temperature, resistivity, and upper and lower critical field measurements made on a single specimen.