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.X27.7
Abstract: X27.00007 : Realizing Half Metallicity in Sr$_{2}$FeMoO$_{6}$ Epitaxial Films: Roadblocks and Successes*
4:30 PM–5:06 PM
Preview Abstract
Abstract
Author:
Fengyuan Yang
(The Ohio State University)
Half-metallic Sr$_{2}$FeMoO$_{6}$ has attracted much attention
due to its
high Tc of 420 K for magnetoelectronic applications. However, the
potential
of its half metallicity is far from being realized due to the
unusual
challenges in the fabrication of Sr$_{2}$FeMoO$_{6}$ films. In
this talk, I
will discuss a number of hurdles that troubled the deposition of
Sr$_{2}$FeMoO$_{6}$ films, some of which have been largely
ignored to date.
We have succeeded in overcoming some of the dominant problems in the
epitaxial film growth and obtained phase-pure, fully epitaxial, and
stoichiometric Sr$_{2}$FeMoO$_{6}$ films on SrTiO$_{3}$ with high
structural
and magnetic ordering using off-axis ultrahigh vacuum sputtering.
First, by
precisely controlling the growth environment, we achieved pure
double
perovskite phase and complete epitaxy in Sr$_{2}$FeMoO$_{6}$
films without
any detectable secondary phases (such as SrMoO$_{4})$ as
confirmed by
Bragg-Brentano and triple-axis X-ray diffraction (XRD) and
aberration-corrected TEM. Secondly, we discovered using Rutherford
backscattering (RBS) that the films have much more Mo than Fe
under typical
growth conditions (high sputter pressure) for complex oxides. The
optimal
pressure for obtaining stoichiometric films is around 10 mTorr at
certain
off-axis geometry. Next, we focused on improving the Fe/Mo
ordering by
tuning growth rate, substrate temperature and sputtering
pressure. To date,
the highest Fe/Mo ordering parameter we have is around 90{\%}
obtained by
Rietveld refinements on epitaxial Sr$_{2}$FeMoO$_{6}$ (111) films
with
ordered double perovskite XRD peaks. More importantly, the
Sr$_{2}$FeMoO$_{6}$ films exhibit strong magnetic shape
anisotropy, i.e. the
in-plane hysteresis loops are fairly square and the out-of-plane
loops are
perfectly slanted lines with a saturation filed of $\sim $3800
Oe. The clear
shape anisotropy, which has never been seen before in
Sr$_{2}$FeMoO$_{6}$
films, indicates strong magnetic coupling across the films. We
are pursuing
further improvement of the Sr$_{2}$FeMoO$_{6}$ film quality and
incorporating it into magnetic heterostructures for magnetotransport
studies.
*Supported by the Center for Emergent Materials at the Ohio State University, a NSF MRSEC (Award Number DMR-0820414).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2010.MAR.X27.7