A S=1/2 vanadium-based geometrically frustrated spinel system Li2ZnV3O8

TL;DR

This study synthesizes and characterizes a new vanadium-based spinel Li2ZnV3O8, revealing strong antiferromagnetic correlations, spin-freezing behavior, and persistent disorder likely due to geometric frustration, with minimal temperature dependence in NMR properties.

Contribution

It introduces a novel Zn-doped LiV2O4 system with only tetravalent vanadium and provides detailed magnetic and NMR characterization highlighting geometric frustration effects.

Findings

Strong antiferromagnetic correlations indicated by Curie-Weiss temperature ~214 K

Spin-freezing observed below 6 K with a peak at 3.5 K in ZFC susceptibility

Significant disorder persists despite large Curie-Weiss temperature, suggesting geometric frustration

Abstract

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 <theta>CW ~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 continued presence of large disorder in the system in spite of the large <theta>CW, which might result from strong geometric frustration in the system. We did not find any temperature T dependence in our 7Li nuclear magnetic resonance NMR shift down to 6 K (an abrupt change in the shift takes place below 6 K) though considerable T-dependence has been found in literature for LiV2O4- undoped or with other Zn/Ti contents. Consistent with the above observation, the 7Li nuclear spin-lattice relaxation rate 1/T1 is relatively small and nearly T-independent except a small increase close to the freezing temperature, once again, small compared to undoped or 10% Zn or 20% Ti-doped LiV2O4.