Magnetic field induced reentrance of superconductivity in the cage-type superconductor Y5Rh6Sn18

Abstract

The morphological and/or chemical disorder is commonly known as detrimental to superconductivity and typically reduces the critical temperature Tc. We present research on the skutterudite-related Y5Rh6Sn18 system, where local atomic disorder leads to novel disorder-enhanced superconductivity. Our present studies focus on the series of Y4.5M0.5Rh6Sn18 compounds, where the metallic dopants M=Ca, Ti, Sr, Zr, La, or Lu, when they are smaller than the atomic radius of Y (the case of Ti, Zr, Lu, or vacancies at the Y sites), generate the so-called peak effect at T<Tc in the fields smaller than the critical field Hc2. The peak effect is well documented experimentally by measurements of the temperature variations in electric transport and ac magnetic susceptibility under external magnetic fields. In accordance with the commonly accepted explanation of the peak effect, we assume that the magnetic field induced reentrance of superconductivity in Y4.5M0.5Rh6Sn18 results from a change in the structure of the vortex lattice close to Hc2. Using a simple theoretical model we argue that the effectiveness of this mechanism can depend on the size of the dopant. We also investigate the band structure properties by x-ray electron spectroscopy and ab initio calculations. It seems interesting that the density functional theory predicts a magnetic moment on the dopant Ti, which is a reason for the Kondo effect, confirmed experimentally.

Source-reported materials — not catalogue approval

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