Surface-phase superconductivity in a Mg-deficient V-doped MgTi2O4 spinel

Abstract

Around 50 years ago, LiTi2O4 was reported to be the only spinel oxide to exhibit a superconducting transition with the highest Tc≈13.7 K. Recently, MgTi2O4 has been found to be another spinel oxide to reveal a superconducting transition with Tc≈3 K, however, its superconducting state is realized only in thin film superlattices involving SrTiO3. We find that a V-doped Mg1−xTi2O4 phase, which gets stabilized as a thin surface layer on top of a nearly stoichiometric and insulating V-doped MgTi2O4 bulk sample, exhibits high-temperature superconductivity with Tc≈16 K. The superconducting transition is also confirmed through a concomitant sharp diamagnetic transition immediately below Tc. The spinel phase of the superconducting surface layer is conformed through grazing-incidence x-ray diffraction and micro-Raman spectroscopy. A small shift of the sharp superconducting transition temperature (∼4 K) with the application of a high magnetic field (up to 9 T) suggests a very high critical field for the system, ∼25 T. Thus, V-doped Mg1−xTi2O4 exhibits the maximum Tc among spinel superconductors and also possesses a very high critical field.

Source-reported materials — not catalogue approval

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