Structural and Magnetic Characterization of NdCaCrO4 Oxide

The structural and magnetic properties of NdCaCrO4 oxide have been studied mainly by means of neutron powder diffraction. This oxide presents orthorhombic symmetry, space group Bmab, with lattice parameters at room temperature a=5.3739(1) ?, b=5.54114(1) ?, and c=11.9536(3) ?. At around 973 K a reversible phase transition to a tetragonal (I4/mmm) structure has been determined from X-ray powder diffraction data. Below 180 K, NdCaCrO4 shows antiferromagnetic ordering in the Cr3+ sublattice that has been explained on the basis of a propagation vector K=0 and a collinear magnetic structure, with a symmetry mode Gx. At 30 K an antiferromagnetic ordered component along the z direction appears. This spin reorientation could be induced by the onset of local magnetic interactions between the neodymium and chromium sublattices.