A Ca substitution study of NaV2O4: High-pressure synthesis of the Na1−xCaxV2O4 solid solution

Ambient pressure CaV2O4 and high-pressure NaV2O4 crystallize in the CaFe2O4 structure type containing double chains of edge-sharing VO6 octahedra. Recent measurements on NaV2O4 reveal low-dimensional metallicity and evidence of half-metallic ferromagnetism. In contrast, CaV2O4 is an antiferromagnetic insulator. To explore the evolution of these ground-state behaviors, we have prepared a series of Ca-doped NaV2O4 compounds with the formula Na1−xCaxV2O4 (x = 0–1) using high-pressure synthesis. Samples at the Na end (x = 0–0.07) show a broad antiferromagnetic transition in the 120–160 K range in accordance with earlier reports. Transport measurements show an insulator–metal transition at x ∼ 0.2. Samples with higher Ca concentrations (x = 0.4–0.7) exhibit a metal–insulator transition around 150 K. The results for the Na1−xCaxV2O4 solid solution is discussed in comparison to existing studies at the Ca- and Na-rich ends.

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