High critical fields in MgB2 thin films with various resistivity values

TL;DR

This study investigates the upper critical magnetic fields of MgB2 thin films with varying resistivity and temperature, revealing linear temperature dependence and multiband effects influencing superconducting properties.

Contribution

It provides new insights into how resistivity and critical fields are related in MgB2 thin films, highlighting the impact of different scattering mechanisms.

Findings

Critical fields range from 13 to 24 T perpendicular to the film.

Linear temperature dependence of Hc2 observed without saturation.

Resistivity values derived from Hc2(T) curves match measured data.

Abstract

In this paper, we analyze the upper critical field of four MgB2 thin films, with different resistivity (between 5 to 50 mWcm) and critical temperature (between 29.5 to 38.8 K), measured up to 28 Tesla. In the perpendicular direction the critical fields vary from 13 to 24 T and we can estimate 42-57 T range in other direction. We observe linear temperature dependence even at low temperatures without saturation, in contrast to BCS theory. Considering the multiband nature of the superconductivity in MgB2, we conclude that two different scattering mechanisms influence separately resistivity and critical field. In this framework, resistivity values have been calculated from Hc2(T) curves and compared with the measured ones.