Thermal Evolution of the Crystallographic and Magnetic Structure in LuVO3: A Neutron Diffraction Study

Polycrystalline LuVO3 perovskite has been studied by neutron powder diffraction (NPD), specific heat, and magnetization measurements. Below TN 107 K, LuVO3 undergoes magnetic ordering according to a canted antiferromagnetic structure. Neutron diffraction data show that the magnetic structure is characterized by the propagation vector k = 0 and the spin arrangement for the V atoms below TN is given by the basis vector (0,Ay,Fz). The magnetic structure remains stable down to 2 K and the ferromagnetic component is very weak, in good agreement with the magnetic measurements. The ordered magnetic moment at T = 2.4 K for the V atoms is 1.33(6)(pi)B. A few degrees below TN, a crystallographic transition is observed, from the orthorhombic room-temperature structure (Pnma space group) to monoclinic (P21\n space group) below the transition. The changes in the crystallographic structure occur between 94 and 82 K. Despite the fact that below 82 K there are two sites for the V atoms, the arrangement of the V-O bonding lengths is the same in the y = 0 plane and in the y = 1\2 layer, so the (010) planes are in phase along the b-direction. This suggests an in-phase orbital ordering of the V t2g orbitals compatible with the A-type magnetic structure