1 research outputs found
Polar Order and Frustrated Antiferromagnetism in Perovskite Pb<sub>2</sub>MnWO<sub>6</sub> Single Crystals
Single crystals of the multiferroic
double-perovskite Pb<sub>2</sub>MnWO<sub>6</sub> have been synthesized
and their structural, thermal, magnetic and dielectric properties
studied in detail. Pure perovskite-phase formation and stoichiometric
chemical composition of the as-grown crystals are confirmed by X-ray
single-crystal and powder diffraction techniques as well as energy-dispersive
X-ray and inductively coupled plasma mass spectrometry. Detailed structural
analyses reveal that the crystals experience a structural phase transition
from the cubic space group (s.g.) <i>Fm</i>3Ì…<i>m</i> to an orthorhombic structure in s.g. <i>Pn</i>2<sub>1</sub><i>a</i> at about 460 K. Dielectric data suggest
that a ferrielectric phase transition takes place at that same temperature,
in contrast to earlier results on polycrystalline samples, which reported
a transition to s.g. <i>Pnma</i> and an antiferroelectric
low-temperature phase. Magnetic susceptibility measurements indicate
that a frustrated antiferromagnetic phase emerges below 8 K. Density
functional theory based calculations confirm that the cationic order
between Mn and W is favorable. The lowest total energy was found for
an antiferromagnetically ordered state. However, analyses of the calculated
exchange parameters revealed strongly competing antiferromagnetic
interactions. The large distance between the magnetic atoms, together
with magnetic frustration, is shown to be the main reason for the
low value of the ordering temperature observed experimentally. We
discuss the structure–property relationships in Pb<sub>2</sub>MnWO<sub>6</sub> and compare these observations to reported results
on related Pb<sub>2</sub>BWO<sub>6</sub> perovskites with different
B cations