1 research outputs found
Observation of Ferroelectricity and Structure-Dependent Magnetic Behavior in Novel One-Dimensional Motifs of Pure, Crystalline Yttrium Manganese Oxides
Multiferroic materials, such as nanostructured <i>h</i>-YMnO<sub>3</sub>, are expected to fulfill a crucial role
as active
components of technological devices, particularly for information
storage. Herein, we report on the template mediated sol–gel
synthesis of unique one-dimensional nanostructured motifs of hexagonal
phase YMnO<sub>3</sub>, possessing a space group of <i>P</i>6<sub>3</sub><i>cm</i>. We found that the inherent morphology
of the as-obtained <i>h</i>-YMnO<sub>3</sub> nanostructures
was directly impacted by the chemical composition of the employed
membrane. Specifically, the use of anodic alumina and polycarbonate
templates promoted nanotube and nanowire formation, respectively.
Isolated polycrystalline nanotubes and single crystalline nanowires
possessed diameters of 276 ± 52 nm, composed of 17 nm particulate
constituent grains, and 125 ± 21 nm, respectively, with lengths
of up to several microns. The structures and compositions of all our
as-prepared products were probed by XRD, SEM, HRTEM, EXAFS, XANES,
SAED, and far-IR spectroscopy. In the specific case of nanowires,
we determined that the growth direction was mainly along the <i>c</i>-axis and that discrete, individual structures gave rise
to expected ferroelectric behavior. Overall, our YMnO<sub>3</sub> samples
evinced the onset of a spin-glass transition at 41 ± 1 K for
both templateless bulk control and nanowire samples but at 26 ±
3 K for nanotubes. Interestingly, only the as-synthesized crystalline
nanotubular mesh gave rise to noticeably enhanced magnetic properties
(i.e., a higher magnetic moment of 3.0 μ<sub>B</sub>/Mn) as
well as a lower spin-glass transition temperature, attributable to
a smaller constituent crystallite size. Therefore, this work not only
demonstrates our ability to generate viable one-dimensional nanostructures
of a significant and commercially relevant metal oxide but also contributes
to an understanding of structure–property correlations in these
systems