APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010;
Portland, Oregon
Session X27: Focus Session: Chemical Control of the Properties of Complex Oxides I
2:30 PM–5:30 PM,
Thursday, March 18, 2010
Room: D137
Sponsoring
Unit:
DCP
Chair: Patrick Woodward, Ohio State University
Abstract ID: BAPS.2010.MAR.X27.4
Abstract: X27.00004 : Chemical control of the properties of perovskite oxides
3:30 PM–4:06 PM
Preview Abstract
Abstract
Author:
Makoto Tachibana
(National Institute for Materials Science)
Perovskite oxides show a variety of interesting properties that
can be tuned by chemical control. In this talk, I will present
three examples of how such approach can be used to study the
nature of functional properties in perovskites:
(1) $R$MnO$_{3}$ ($R$=rare earth) show a variety of unusual
states, including the spiral spin ordering and ferroelectricity
in $R$=Tb and Dy. In [1], $R$=Ho-Lu have been obtained under high
pressure, and their magnetic and structural properties have been
studied. Combined with the data on larger $R$, the results
show the importance of competing magnetic interactions on the
complex phase diagram of $R$MnO$_{3}$.
(2) $R$CoO$_{3}$ show a spin-state transition and an
insulator-metal transition as a function of temperature. The
nature of the excited states has been studied since the 1950's,
but remains elusive. Here [2], I provide the complete electronic
phase diagram of $R$CoO3 that has been obtained from
high-pressure synthesis and heat capacity measurements. The
results support a picture involving a high-spin state above the
spin-state transition and an intermediate-spin state above the
insulator-metal transition.
(3) Pb(Mg$_{1/3}$Nb$_{2/3})$O$_{3}-x$PbTiO$_{3}$ (PMN-$x$PT) is a
relaxor ferroelectric system with extraordinary dielectric and
piezoelectric properties. The average structure of the system
changes from cubic to rhombohedral, monoclinic, and tetragonal
with $x$. However, this system is also characterized by nanoscale
phase inhomogeneities, and the role of polar nanoregions on the
enhanced properties is not clear. Here [3], I will show that
thermal conductivity and heat capacity of PMN-$x$PT show a
systematic evolution from glasslike to crystalline behavior as a
function of $x$. The results provide interesting perspectives on
how polar nanoregions are transformed into macroscopic
polarizations with increasing $x$.
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[1] M. Tachibana et al., Phys. Rev. B 75, 144425 (2007).
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[2] M. Tachibana et al., Phys. Rev. B 77, 094402 (2008).
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[3] M. Tachibana et al., Phys. Rev. B 79, 100104(R) (2009).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2010.MAR.X27.4