Abstract
We have expanded the double perovskite family
of materials with the unusual combination of layered order in
the A sublattice and rock salt order over the B sublattice to
compounds NaLaFeWO6 and NaNdFeWO6. The materials
have been synthesized and studied by powder X-ray diffraction,
neutron diffraction, electron diffraction, magnetic measurements,
X-ray absorption spectroscopy, dielectric measurements,
and second harmonic generation. At room temperature, the
crystal structures of both compounds can be defined in the
noncentrosymmetric monoclinic P21 space group resulting
from the combination of ordering both in the A and B
sublattices, the distortion of the cell due to tilting of the
octahedra, and the displacement of certain cations. The
magnetic studies show that both compounds are ordered antiferromagnetically below TN ≈ 25 K for NaLaFeWO6 and at
∼21 K for NaNdFeWO6. The magnetic structure of NaNdFeWO6 has been solved with a propagation vector k = (1/2 0 1/2) as an
antiferromagnetic arrangement of Fe and Nd moments. Although the samples are potential multiferroics, the dielectric
measurements do not show a ferroelectric response.
