AC loss in granular superconducting MgB2 at radio frequencies

TL;DR

This study investigates the ac loss behavior of granular MgB2 superconductors at radio frequencies, highlighting the influence of two-band gaps, Josephson junctions, and sample properties on energy dissipation.

Contribution

It provides new insights into the frequency, amplitude, and sample condition dependence of ac losses in MgB2, emphasizing the role of Josephson junction decoupling.

Findings

AC loss pattern differs from other high Tc superconductors due to two-band gaps.

Josephson junction decoupling significantly affects ac loss in MgB2.

Sample properties like grain size and pressure influence ac loss behavior.

Abstract

AC losses of granular superconducting MgB2 were measured using non-resonant rf power absorption techniques. The presence of two band-gaps makes the temperature dependent ac loss pattern of MgB2 different from other high Tc superconductors like YBa2Cu3O and BSCCO-2223. Josephson junction decoupling plays a major role in MgB2 polycrystalline samples, both in the presence and absence of magnetic field. We studied the ac loss of MgB2 samples with different crystalline properties, grain sizes and pressures and sintered under different physical and chemical conditions. The effects of frequency and amplitude of ac current on the ac loss are discussed in detail.