7 research outputs found
Optical spectroscopic investigation on the coupling of electronic and magnetic structure in multiferroic hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films
We investigated the effects of temperature and magnetic field on the
electronic structure of hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films
using optical spectroscopy. As the magnetic ordering of the system was
disturbed, a systematic change in the electronic structure was commonly
identified in this series. The optical absorption peak near 1.7 eV showed an
unexpectedly large shift of more than 150 meV from 300 K to 15 K, accompanied
by an anomaly of the shift at the Neel temperature. The magnetic field
dependent measurement clearly revealed a sizable shift of the corresponding
peak when a high magnetic field was applied. Our findings indicated strong
coupling between the magnetic ordering and the electronic structure in the
multiferroic hexagonal RMnO3 compounds.Comment: 16 pages including 4 figure
Electronic structures of hexagonal RMnO3 (R = Gd, Tb, Dy, and Ho) thin films
We investigated the electronic structure of multiferroic hexagonal RMnO3 (R =
Gd, Tb, Dy, and Ho) thin films using both optical spectroscopy and
first-principles calculations. Using artificially stabilized hexagonal RMnO3,
we extended the optical spectroscopic studies on the hexagonal multiferroic
manganite system. We observed two optical transitions located near 1.7 eV and
2.3 eV, in addition to the predominant absorption above 5 eV. With the help of
first-principles calculations, we attribute the low-lying optical absorption
peaks to inter-site transitions from the oxygen states hybridized strongly with
different Mn orbital symmetries to the Mn 3d3z2-r2 state. As the ionic radius
of the rare earth ion increased, the lowest peak showed a systematic increase
in its peak position. We explained this systematic change in terms of a
flattening of the MnO5 triangular bipyramid
Interface Control of Ferroelectricity in an SrRuO3/BaTiO3/SrRuO3 Capacitor and its Critical Thickness
The atomic-scale synthesis of artificial oxide heterostructures offers new
opportunities to create novel states that do not occur in nature. The main
challenge related to synthesizing these structures is obtaining atomically
sharp interfaces with designed termination sequences. In this study, it is
demonstrated that the oxygen pressure (PO2 ) during growth plays an important
role in controlling the interfacial terminations of SrRuO3/BaTiO3/SrRuO3
(SRO/BTO/SRO) ferroelectric (FE) capacitors. The SRO/BTO/SRO heterostructures
are grown by a pulsed laser deposition method. The top SRO/BTO
interface, grown at high PO2 (around 150 mTorr), usually exhibits a mixture of
RuO2–BaO and SrO–TiO2 terminations. By reducing PO2, the authors obtain
atomically sharp SRO/BTO top interfaces with uniform SrO–TiO2 termination.
Using capacitor devices with symmetric and uniform interfacial termination,
it is demonstrated for the first time that the FE critical thickness can
reach the theoretical limit of 3.5 unit cells.
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