Upper critical fields of MgB2 thin films

TL;DR

This study measures the upper critical magnetic fields of MgB2 thin films up to 28 T, revealing high and anisotropic critical fields that are influenced by multiband effects and scattering mechanisms.

Contribution

It provides new high-field measurements of MgB2 thin films and analyzes the influence of multiband superconductivity on critical fields.

Findings

Critical fields up to 24 T (c-axis) and 57 T (basal plane) were observed.

Hc2(T) curves are linear at low temperatures.

Resistivity and critical fields are affected by different scattering mechanisms.

Abstract

Critical fields of four MgB2 thin films with a normal state resistivity ranging from 5 to 50 mWcm and Tc from 29.5 to 38.8 K were measured up to 28 T. Hc2(T) curves present a linear behavior towards low temperatures. Very high critical field values have been found, up to 24 T along the c-axis and 57 T in the basal plane not depending on the normal state resistivity values. In this paper, critical fields will be analyzed taking into account the multiband nature of MgB2; we will show that resistivity and upper critical fields can be ascribed to different scattering mechanisms.