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Title: Spectroscopic Determination of Phase in Tetragonally Strained Ba0.5Sr0.5TiO3 Films at Room Temperature

Abstract

Sputter-deposited Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} thin films on MgO(001) substrates with either in-plane (c<a) or out-of-plane (c>a) tetragonal lattice structure distortions were characterized by polarization-dependent Ti K-edge x-ray absorption fine-structure (XAFS) spectroscopy and microwave dielectric measurements. Anisotropy between the in-plane and out-of-plane directions in the films as determined by XAFS provided evidence of spontaneous polarization, and the anisotropy varied with the type of structural distortion. These results explain microwave measurements in which the dielectric properties were significantly affected by lattice distortions and exhibited hysteresis in the in-plane dielectric constant with dc bias at room temperature, suggesting the presence of permanent dipoles.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930524
Report Number(s):
BNL-80549-2008-JA
Journal ID: ISSN 0003-6951; APPLAB; TRN: US200904%%767
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 91
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; AMBIENT TEMPERATURE; ANISOTROPY; DIELECTRIC MATERIALS; DIELECTRIC PROPERTIES; DIPOLES; FINE STRUCTURE; HYSTERESIS; PERMITTIVITY; POLARIZATION; SPECTROSCOPY; SUBSTRATES; TETRAGONAL LATTICES; THIN FILMS; X-RAY SPECTROSCOPY; national synchrotron light source

Citation Formats

Alldredge,L., Woicik, J., Chang, W., Kirchoefer, S., and Pond, J. Spectroscopic Determination of Phase in Tetragonally Strained Ba0.5Sr0.5TiO3 Films at Room Temperature. United States: N. p., 2007. Web. doi:10.1063/1.2766668.
Alldredge,L., Woicik, J., Chang, W., Kirchoefer, S., & Pond, J. Spectroscopic Determination of Phase in Tetragonally Strained Ba0.5Sr0.5TiO3 Films at Room Temperature. United States. doi:10.1063/1.2766668.
Alldredge,L., Woicik, J., Chang, W., Kirchoefer, S., and Pond, J. Mon . "Spectroscopic Determination of Phase in Tetragonally Strained Ba0.5Sr0.5TiO3 Films at Room Temperature". United States. doi:10.1063/1.2766668.
@article{osti_930524,
title = {Spectroscopic Determination of Phase in Tetragonally Strained Ba0.5Sr0.5TiO3 Films at Room Temperature},
author = {Alldredge,L. and Woicik, J. and Chang, W. and Kirchoefer, S. and Pond, J.},
abstractNote = {Sputter-deposited Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} thin films on MgO(001) substrates with either in-plane (c<a) or out-of-plane (c>a) tetragonal lattice structure distortions were characterized by polarization-dependent Ti K-edge x-ray absorption fine-structure (XAFS) spectroscopy and microwave dielectric measurements. Anisotropy between the in-plane and out-of-plane directions in the films as determined by XAFS provided evidence of spontaneous polarization, and the anisotropy varied with the type of structural distortion. These results explain microwave measurements in which the dielectric properties were significantly affected by lattice distortions and exhibited hysteresis in the in-plane dielectric constant with dc bias at room temperature, suggesting the presence of permanent dipoles.},
doi = {10.1063/1.2766668},
journal = {Applied Physics Letters},
number = ,
volume = 91,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The dielectric properties of sputter-deposited Ba{sub 1-x}Sr{sub x}TiO{sub 3} (BST) thin films on (001) MgO substrates with in-plane or out-of-plane tetragonal lattice structure distortions were characterized as a function of temperature. A temperature-dependent interpolation calibration technique was developed for increased efficiency of the microwave measurements. The BST films showed significant differences in the ferroelectric phase transition due to lattice distortions with a strong temperature dependence of the in-plane dielectric behavior for films under tensile strain and a weak temperature dependence for films under compressive strain. The experimental data agreed well with theoretical modeling of the BST film strain effect basedmore » on Devonshire's theory.« less
  • In this study, highly strained films of BiFe 0.5Mn 0.5O 3 (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetization measurements demonstrated ferrimagnetism (T C ~ 600K), with a room temperature saturation moment (M S) of up to 90 emu/cc (~0.58μ B/f.u) on high quality (001) SrTiO 3. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe 3+ and Mn 3+ . While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magneticmore » properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.« less
  • In this study, highly strained films of BiFe 0.5Mn 0.5O 3 (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetization measurements demonstrated ferrimagnetism (T C ~ 600K), with a room temperature saturation moment (M S) of up to 90 emu/cc (~0.58μ B/f.u) on high quality (001) SrTiO 3. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe 3+ and Mn 3+ . While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magneticmore » properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.« less