Quasi-two-dimensional vortex–glass transition and the critical current density in TiO epitaxial thin films

Abstract

There are many fascinating properties in titanium oxides such as the enhanced superconductivity in cubic TiO epitaxial thin films with the superconducting transition temperature of 7.65 K, which is much higher than that of the bulk polycrystalline TiO. To explore the superconductivity of the TiO thin films in more detail, we investigated the magnetic field and temperature dependences of the current–voltage (I–V) characteristics and the critical current density Jc in magnetic fields perpendicular to the film surface. The I–V curves show a quasi-two-dimensional vortex glass (VG) scaling collapse in different magnetic fields, and a vortex phase diagram is constructed from the VG and vortex liquid regions to the normal state. Through the critical current density investigation, we found that δl pinning dominates the pinning behavior, which is in accordance with the analyzed results of the vortex pinning force associated with defects in the film, such as grain boundaries. The findings of the magnetic phase diagram and critical current properties should be helpful for practical applications of the TiO family.