Li2ZnV3O8: a vanadium-based geometrically frustrated spinel system

We report the synthesis and characterization of Li2ZnV3O8, which is a new Zn-doped LiV2O4 system containing only tetravalent vanadium. A Curie-Weiss susceptibility with a Curie-Weiss temperature of θCW ≈ -214 K suggests the presence of strong antiferromagnetic correlations in this system. We have observed a splitting between the zero-field cooled (ZFC) and field cooled (FC) susceptibility curves below 6 K. A peak is present in the ZFC curve around 3.5 K, suggestive of spin-freezing. Similarly, a broad hump is also seen in the inferred magnetic heat capacity around 9 K. The consequent entropy change is only about 8% of the value expected for an ordered S = 1/2 system. This reduction indicates the continued presence of large disorder in the system in spite of the large θCW, which might result from strong geometric frustration in the system. We did not find any temperature T dependence in our (7)Li nuclear magnetic resonance shift down to 6 K (an abrupt change in the shift does take place below 6 K), though considerable T-dependence has been found in the literature for LiV2O4--undoped or with other Zn/Ti contents. Consistent with the above observation, the (7)Li nuclear spin-lattice relaxation rate 1/T1 is relatively small and nearly T-independent, except for a small increase close to the freezing temperature which, once again, is small compared to undoped or 10% Zn or 20% Ti-doped LiV2O4.