## Abstract

Two new CaFe<inf>2</inf>O<inf>4</inf>-type compounds NaV<inf>1.25</inf>Ti<inf>0.75</inf>O<inf>4</inf> (1) and NaVSnO<inf>4</inf> (2) have been prepared at ambient pressure and temperatures < 800 °C. This contrasts with the parent material NaV<inf>2</inf>O<inf>4</inf> which is synthesized at 6 GPa and 1300 °C. The lattice parameters are a = 9.1500(4) Å, b = 2.9399(3) Å, and c = 10.6568(5) Å for 1 and a = 9.3083(6) Å, b = 3.0708(2) Å, and c = 10.9194(5) Å for 2 (space group Pnma). Structure refinement against neutron powder diffraction data reveals that V/Ti and V/Sn are disordered over two octahedral sites. Both materials are characterized by a magnetic transition near 150 K below which the Curie moment is reduced from a value consistent with V<sup>3+</sup> [0.75 emu mol<inf>V</inf><sup>-1</sup> K<sup>-1</sup> for 1 and 0.58 emu mol<inf>V</inf><sup>-1</sup> K<sup>-1</sup> for 2] to 0.23 emu mol<inf>V</inf><sup>-1</sup> K<sup>-1</sup> for 1 and 0.30 emu mol<inf>V</inf><sup>-1</sup> K<sup>-1</sup> for 2, signaling a 70-50% reduction in the paramagnetic moment. The Weiss temperature (θ) is reduced from -285 (1) and -138 K (2) to values close to 0 K, suggesting that the remaining spins are dilute and weakly interacting. Heat capacity measurements reveal a gradual loss of magnetic entropy between 2 and 150 K, consistent with short-range bulk magnetic ordering. In addition, heat capacity and magnetic susceptibility measurements reveal a number of weak magnetic transitions below 6 K involving both antiferromagnetic and ferromagnetic components.

Original language | English |
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Pages (from-to) | 7264-7271 |

Number of pages | 8 |

Journal | Inorganic Chemistry |

Volume | 54 |

Issue number | 15 |

DOIs | |

Publication status | Published - 3 Aug 2015 |

## ASJC Scopus subject areas

- Inorganic Chemistry
- Physical and Theoretical Chemistry