Comparison of the Temperature Dependence of the Crystal Structure of LiTi2O4 and LiV2O4

E.G. Moshopoulou Institute of Materials Science, National Center for Scientific Research, "Demokritos", 15310 Agia Paraskevi, Greece

Full Text PDF

Received: 9 07 2007;

The normal spinel oxide LiTi2O4 is an exotic superconductor with Tc=11.2 K, while the isostructural neighbouring LiV2O4 exhibits heavy-fermion behaviour. The origin of their physics and the role of the spinel structure on their properties are yet unsolved issues, owing mainly to the complexity of the structure, the presence of subtle disorder, and the sample dependence of the physical properties. Especially and perhaps more importantly, the enormous difference in their low-temperature properties remains an open question. This question has only been addressed theoretically but (mainly because of the above problems) there were no experimental studies that sought to understand the clearly distinct behaviour of the two systems. Here, we contribute to the understanding of such distinct low-temperature behaviour by comparing the temperature dependence of the very basic structural properties of the two systems. Upon cooling from room temperature, the lattice parameter a decreases gradually in about the same way for both systems. However, below 20 K, a clear decrease in a of LiV2O4 as a function of temperature contrasts strongly with the almost constant value of a of LiTi2O4 in the same temperature range. Therefore subtle but clearly different structural signatures are coupled with the very divergent physical properties of the two systems and suggest new directions to the theory.

DOI: 10.12693/APhysPolA.113.399 PACS numbers: 74.70.-b, 61.05.fm