APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014;
Denver, Colorado
Session M6: Focus Session: Magnetic Oxide Thin Films and Heterostructures: Ferroelectric Effects
11:15 AM–2:15 PM,
Wednesday, March 5, 2014
Room: 108
Sponsoring
Units:
DMP GMAG
Chair: Yu-Miin Sheu, Los Alamos National Laboratory
Abstract ID: BAPS.2014.MAR.M6.5
Abstract: M6.00005 : Spin-phonon coupling and ferroelectricity in magnetoelectric gallium ferrite*
12:27 PM–1:03 PM
Preview Abstract
Abstract
Author:
Somdutta Mukherjee
(SSCU, Indian Institute of Science, Bangalore)
Gallium ferrite (GaFeO$_{3}$ or GFO) is a low temperature
ferrimagnet and room temperature piezoelectric wherein the magnetic
transition temperature (T$_{\mathrm{C}})$ could be tailored to room
temperature and above by tuning the stoichiometry and processing conditions.
Such tunability of the magnetic transition temperature renders GFO a unique
perspective in the research of multiferroics to potentially demonstrate room
temperature magnetoelectric effect attractive for futuristic digital memory
applications. Recent studies in several transition metal oxides highlight
the importance of spin-phonon coupling in designing novel multiferroics by
means of strain induced phase transition.
In the present work, we have systematically studied the evolution of phonons
in good quality samples of GFO across the T$_{\mathrm{C}}$ using Raman
spectroscopy. Using the phonon softening behavior and nearest neighbor
spin-spin correlation function below T$_{\mathrm{C}}$ we estimated
spin-phonon coupling strength in the magnetically ordered state. In the
process, we also show, for the first time, the presence of a spin glass
phase in GFO where the spin-glass transition has a signature of abrupt
change in spin-phonon coupling strength.
Though GFO is piezoelectric and crystallizes in polar Pc2$_{1}$n
symmetry, its ferroelectric nature remained controversial probably due to
the large leakage current in the bulk material. To address this issue, we
deposited epitaxial thin film on single crystalline yttria stabilized
zirconia (YSZ) substrate using indium tin oxide (ITO) as a bottom conducting
layer. We demonstrate clear evidence of room temperature ferroelectricity in
the thin films from the 180$^{\mathrm{o}}$ phase shift of the piezoresponse
upon switching the electric field. Further, suppression of dielectric
anomaly in presence of an external magnetic field clearly reveals a
pronounced magneto-dielectric coupling across the magnetic transition
temperature. In addition, using first principles calculations we elucidate
that Fe ions are not only responsible for ferrimagnetism as observed
earlier, but give rise to the observed ferroelectricity also, making GFO an
unique single phase multiferroic.
*I thank to my collaborators (Somdutta Mukherjee, Amritendu Roy, Sushil Auluck, Rajendra Prasad, Rajeev Gupta,and Ashish Garg) for their contributions in the present work. This work was partially funded by DST, India.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.MAR.M6.5