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 orthorho mbic symmetry, space group Bmab with lattice parameters nt room temperature a = 5.3739(1) Angstrom, b = 5.54114(1) Angstrom, and c = 11.9536(3) Angstr om. 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 h as been explained on the basis of a propagation vector k = 0 and a collinea r magnetic structure, with a symmetry mode G(x). At 30 K an antiferromagnet ic ordered component along the z direction appears. This spin reorientation could be induced by the onset of local magnetic interactions between the n eodymium and chromium sublattices. (C) 1999 Academic Press.