Abstract:
A systematic comparative analysis of the effect of the upper buffer layer on the transport characteristics of composite high-temperature superconducting tapes is performed. Two most common materials, cerium dioxide CeO$_2$ and lanthanum manganite LaMnO$_3$, are studied. It is shown that replacing CeO$_2$ with LaMnO$_3$ leads to an increase in the characteristic thickness of the superconducting layer, on which the critical current density drops by a factor of e, from 0.9 to 1.2 $\mu$m. When the external magnetic field is oriented in the plane of the tape, samples of both architectures showed the same critical current. When the field is oriented perpendicularly, samples with LaMnO$_3$ demonstrated higher critical currents, which indicates an increase in the concentration of pinning centers perpendicular to the tape plane. Due to the lack of self-epitaxy for LaMnO$_3$, it cannot completely replace CeO$_2$ on substrates with a moderate texture.
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