Long-range antiferromagnetic ordering in theS=12ordered rocksalt oxideLi5OsO6: Comparison with the isoelectronic and isostructural spin glassLi4MgReO6Journal Articles
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abstract
Li5OsO6 and Li5ReO6 polycrystalline samples were synthesized by conventional
solid state methods. Employing powder neutron diffraction data, the crystal
structure of Li5OsO6 was re-investigated. Li5OsO6 crystallizes in C2/m space
group in an ordered NaCl structure type where a = 5.0472(1) A, b = 8.7827(2) A,
c = 5.0079(1) A, Beta = 109.777(2) degree and V = 208.90(1).A^3 Magnetic
susceptibility and heat capacity data indicate an AFM long range order below
40K although there is evidence for low dimensional short range order above 80K.
As well, the frustration index, f = |theta|/TN ~1, in contrast to the
isostructural and isoelectronic compound, Li4MgReO6, which is a spin glass
below 12K and has f ~ 14. An attempt was made to rationalize these differences
using spin dimer analysis. The key results are that the spin exchange
interactions in the Re-based compound are stronger and are consistent with a
frustrated triangular lattice model while a low dimensional short range order
model is better for Li5OsO6. The main reason for this is a strong Jahn-Teller
distortion in the OsO6 octahedron material which constrains the unpaired
electron to occupy the dxy orbital.
