La2MnVO6 double perovskite: a structural, magnetic and X-ray absorption investigation
Journal of Materials Chemistry
The synthesis, electron diffraction (ED), synchrotron X-ray and neutron structure, X-ray absorption spectroscopy (XAS) and magnetic property studies of La 2 MnVO 6 double perovskite are described. Analysis of the synchrotron powder X-ray diffraction data for La 2 MnVO 6 indicates a disordered arrangement of Mn and V at the B-site of the perovskite structure. Absence of super-lattice reflections in the ED patterns for La 2 MnVO 6 supports the disordered cation arrangement. Room temperature
... m temperature time-of-flight (TOF) neutron powder diffraction (NPD) data show no evidence of cation ordering, in corroboration with the ED and synchrotron studies (orthorhombic Pnma, a ¼ 5.6097(3), b ¼ 7.8837(5) and c ¼ 5.5668(3) Å ; 295 K, NPD). A comparison of XAS analyses of La 2 TVO 6 with T ¼ Ni and Co shows T 2+ formal oxidation state while the T ¼ Mn material evidences a Mn 3+ admixture into a dominantly Mn 2+ ground state. V-K edge measurements manifest a mirror image behavior with a V 4+ state for T ¼ Ni and Co with a V 3+ admixture arising in the T ¼ Mn material. The magnetic susceptibility data for La 2 MnVO 6 show ferromagnetic correlations; the observed effective moment, m eff (5.72 m B ) is much smaller than the calculated moment (6.16 m B ) based on the spin-only formula for Mn 2+ (d 5 , HS) /V 4+ (d 1 ), supportive of the partly oxidized Mn and reduced V scenario (Mn 3+ /V 3+ ).