Epitaxial thin films of the superconducting spinel oxide LiTi$_{2}$O$_{4}$

Lithium titanate is the only superconducting spinel oxide documented in literature. Related oxide spinels[1] such as the heavy fermion system LiV$_{2}$O$_{4}$ and charge-ordered LiMn$_{2}$O$_{4}$ indicate that electron correlations are strong in these systems. We have fabricated epitaxial films of LiTi$_{2}$O$_{4}$ on MgAl$_{2}$O$_{4}$ and MgO single crystalline substrates to explore such behavior in thin film form. Atomic force microscopy indicates $<$1nm RMS surface roughness, and 2- and 4-circle x-ray diffraction confirms film epitaxy. Films on MgAl$_{2}$O$_{4}$ have a critical temperature T$_{c}$ of up to 11.3K with a resistivity transition width of 0.25K, while films on MgO have lower T$_{c}$ with broader transitions. Magnetization vs. magnetic field of a zero-field cooled sample shows Meissner shielding consistent with Type II superconductors. Such films can be used in spin-polarization measurements of complex oxide half-metallic thin films, as well as fundamental studies of the effect of epitaxial strain, microstructure, and cation disorder/substitution on the superconducting properties of LiTi$_{2}$O$_{4}$. [1] M. Lauer et al, Phys Rev B 69, 075117 (2004).