paper

Surface-phase superconductivity in Mg-deficient V-doped MgTi $_{2}$ O $_{4}$ spinel

arXiv:2209.02053 · doi:10.1103/PhysRevB.107.245124

Abstract

Around fifty years ago, LiTi $_{2}$ O $_{4}$ was reported to be first spinel oxide to exhibit a superconducting transition with highest T $_{c}$ $\approx$ 13.7 K. Recently, MgTi $_{2}$ O $_{4}$ has been found to be the only other spinel oxide to reveal a superconducting transition with a T $_{c}$ $\approx$ 3 K, however, its superconducting state is realized only in thin film superlattices involving SrTiO $_{3}$ . We find that a V-doped Mg $_{1 - x}$ Ti $_{2}$ O $_{4}$ phase, which gets stabilized as a thin surface layer on top of stoichiometric and insulating V-doped MgTi $_{2}$ O $_{4}$ bulk sample, exhibits high-temperature superconductivity with T $_{c}$ $\approx$ 16 K. The superconducting transition is also confirmed through a concomitant sharp diamagnetic transition immediately below T $_{c}$ . The spinel phase of the superconducting surface layer is elucidated through grazing-incidence X-ray diffraction and Micro-Raman spectroscopy. A small shift of the sharp superconducting transition temperature ( $\sim$ 4 K) with application of a high magnetic field (upto 9 Tesla) suggests a very high critical field for the system, $\sim$ 25 Tesla. Thus, V-doped Mg $_{1 - x}$ Ti $_{2}$ O $_{4}$ exhibits the highest T $_{c}$ among spinel superconductors and also possesses a very high critical field.

5 pages, 4 figures

Surface-phase superconductivity in Mg-deficient V-doped MgTi2​O4​ spinel

Abstract

Surface-phase superconductivity in Mg-deficient V-doped MgTi $_{2}$ O $_{4}$ spinel