Effect of doping on irreversible Campbell length in MgB${}_2$ single crystals

Abstract

We have measured small-amplitude rf penetration depth $\lambda (H,T)$ in pure and C, Li and (Li+C) doped single crystals of MgB${}_2$. The effect of doping on the critical temperature T${}_c$ and on the upper critical field H${}_{c2}$ was found to be in good agreement with previous results. We report the presence of clear signatures of irreversibility in $\lambda (H,T)$, associated with the peak effect. Carbon doping enhances the signature and shifts its position on the H-T phase diagram to higher temperatures. Contrary to this, Li substitution has the effect of suppressing the peak effect to lower temperatures. Analysis of both zero field (ZFC) and field cooled (FC) measurements suggests that the hysteresis associated with the peak effect is due to macroscopic screening supercurrents, $j$, generated during the magnetic field ramp.

References in corpus (4)

• Carbon substitution in MgB2 single crystals: structural and superconducting properties
• Al substitution in MgB2 crystals: influence on superconducting and structural properties
• Fate of the Peak Effect in a Type-II Superconductor: Multicriticality in the Bragg-Glass Transition
• MgB2 single crystals substituted with Li and with Li-C: Structural and superconducting properties