Crystal structure and magnetic properties of Li,Cr-containing molybdates Li3Cr(MoO4)3, LiCr(MoO4)2 and Li1.8Cr1.2(MoO4)3

Single crystals of LiCr(MoO4)2, Li3Cr(MoO4)3 and Li1.8Cr1.2(MoO4)3 were grown by a flux method during the phase study of the Li2MoO4–Cr2(MoO4)3 system at 1023 K. LiCr(MoO4)2 and Li3Cr(MoO4)3 single phases were synthesized by solid-state reactions. Li3Cr(MoO4)3 adopts the same structure type as Li3In(MoO4)3 despite the difference in ionic radii of Cr3+ and In3+ for octahedral coordination. Li3Cr(MoO4)3 is paramagnetic down to 7 K and shows a weak ferromagnetic component below this temperature. LiCr(MoO4)2 is isostructural with LiAl(MoO4)2 and orders antiferromagnetically below 20 K. The magnetic structure of LiCr(MoO4)2 was determined from low-temperature neutron diffraction and is based on the propagation vektor k⇒=(12,12,0). The ordered magnetic moments were refined to 2.3(1) μB per Cr-ion with an easy axis close to the [1 1 1¯] direction. A magnetic moment of 4.37(3) μB per Cr-ion was calculated from the Curie constant for the paramagnetic region.The crystal structures of the hitherto unknown Li1.8Cr1.2(MoO4)3 and LiCr(MoO4)2 are compared and reveal a high degree of similarity: In both structures MoO4-tetrahedra are isolated from each other and connected with CrO6 and LiO5 via corners. In both modifications there are Cr2O10 fragments of edge-sharing CrO6-octahedra.

Magnetic structure of LiCr(MoO4)2. The orientation of the magnetic moments of Cr3+ are shown by arrows.Figure optionsDownload as PowerPoint slide