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Search Publications by Peter M. Gehring

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Displaying 1 - 25 of 26

Decoupled Molecular and Inorganic Framework Dynamics in CH 3 NH 3 PbCl 3

December 30, 2019
M. Songvilay, Zitian Wang, Victoria Garcia Sakai, T. Guidi, M. Bari, Zuo-Guang Ye, Guangyong NMN Xu, K. L. Brown, Peter M. Gehring, Christopher Stock
The organic-inorganic lead halide perovskites are composed of organic molecules embedded in an inorganic framework. The compounds with general formula CH3NH3PbX3 (MAPbX2) display large photovoltaic efficiencies for halogens X=Cl, Br, and I in a wide

Anharmonic Acoustic Phonons and A-site Critical Fluctuations in the Lead Halide Perovskite CsPbBr 3

September 17, 2019
M. Songvilay, Nathan Giles-Donovan, M. Bari, Z.-G. Ye, J. L. Minns, M. A. Green, Guangyong NMN Xu, Peter M. Gehring, K. Schmalzl, William D. Ratcliff, Craig Brown, D. Chernyshov, W. van Beek, Sandy Cochran, Christopher Stock
We apply neutron spectroscopy to investigate the transverse acoustic phonons in the lead halide CsPbBr3 near the three zone boundaries of the cubic Pm3m Brillouin zone at QX = (2,1/2,0), QM = (3/2,1/2,0), and QR = (1/2,1/2,3/2). CsPbBr3 undergoes two

Electric Field Effect on Short-Range Polar Order in a Relaxor Ferroelectric System

July 30, 2019
Zhijun Xu, Fei Li, Shujun Zhang, Christopher Stock, Jun Luo, Peter M. Gehring, Guangyong NMN Xu
Short-range polar orders in the relaxor ferroelectric material PbMg1/2Nb2/3O3-28%PbTiO3 (PMN-28PT) have been studied using neutron diffuse scattering. An external electric field along [110] direction can affect the diffuse scattering in the low temperature

Comment on "Giant Electromechanical Coupling of Relaxor Ferroelectrics Controlled by Polar Nanoregion Vibrations"

March 22, 2019
Peter M. Gehring, Zhijun NMN Xu, C. Stock, Guangyong NMN Xu, Daniel E Parshall, Leland Weldon Harriger, C. A. Gehring, Xiaobing Li, Haosu Luo
Manley et al. (Science Advances, 16 September 2016, p.e1501814) report a splitting of a transverse acoustic phonon branch below Tc in the relaxor ferroelectric Pb[(Mg1/3Nb2/3)1-xTix]O3 with x=0.30 using neutron scattering methods. They argue that this

The Relation of Local Order to Material Properties in Relaxor Ferroelectrics

June 25, 2018
Matthew Krogstad, Peter M. Gehring, Stephan Rosenkranz, Raymond Osborn, Feng Ye, Yaohua Liu, Jacob P. C. Ruff, Wenzhi Chen, Justin M. Wozniak, Haosu Luo, O. Chmaissem, Zuo-Guang Ye, Daniel Phelan
Four different forms of local order that give rise to diffuse neutron and x-ray scattering in the relaxor ferroelectric series PMN-xPT are identified via broad, three-dimensional surveys of reciprocal space. Composition and temperature-dependent

Depth Dependant Element Analysis of PbMg 1/3 Nb 2/3 O 3 using Muonic X-rays

February 28, 2018
Katherine L Brown, Chris PJ Stockdale, Haosu Luo, X Zhao, Jiefang Li, Dwight Viehland, Guangyong NMN Xu, Peter M. Gehring, K Ishida, A. D. Hillier, C. Stock
The relaxor PbMg1.3Nb2/3O3 (PMN) has received attention due to its potential applications as a piezoelectric when doped with PbTiO3 (PT). Previous results have found that there are two phases existing in the system, one linked to the near-surface regions

Spontaneous Decay of a Soft Optical Phonon in the Relaxor Ferroelectric PbMg 1/3 Nb 2/3 O 3

February 13, 2018
C. Stock, Peter M. Gehring, R. A. Ewings, Guangyong NMN Xu, Jiefang Li, Dwight Viehland, Haosu Luo
We report the spontaneous decay of a soft, optical phonon in a solid. Using neutron spectroscopy, we find that specific phonon lifetimes in the relaxor PbMg1/3Nb2/3O3 are anomalously short within well-defined ranges of energy and momentum. This behavior is

Correspondence: Phantom Phonon Localization in Relaxors

December 5, 2017
Peter M. Gehring, Daniel E Parshall, Leland Weldon Harriger, Christopher Stock, Guangyong Xu, Xiaobing Li, Haosu Luo
Manley et al. (Ref. [1]) report the observation of an unexpected, weak, phonon mode located in energy between that of the transverse acoustic (TA) and soft transverse optic (TO) modes in the relaxor ferroelectric Pb[(Mg0.33Nb0.67)1-xTix]O3 (PMN-xPT) with

Fragile Morphotropic Phase Boundary and Phase Stability in the Near-Surface Region of Relaxor Ferroelectric (1-x)Pb(Zn 1/3 Nb 2/3 )O 3-x PbTiO 3 : [001] Field-Cooled Phase Diagrams

November 10, 2016
Yaojin Wang, Ding Wang, Guoliang Yuan, He Ma, Feng Xu, Jiefang Li, D. Viehland, Peter M. Gehring
We have examined the effects of field cooling on the phase diagram of the relaxor system (1-X)Pb(Zn1/3Nb2/3)O6d3-x^PbTiO3 (PZN-xPT) for compositions near the morphotropic phase boundary (MPB). High-resolution diffraction measurements using CuKαx-rays

Neutron Scattering Study of Spin Ordering and Stripe Pinning in Superconducting La 1.93Sr d0.07^CuO 4

November 20, 2015
H. Jacobsen, I. A. Zaliznyak, A. T. Savici, B. L. Winn, S. Chang, M. Hucker, G. D. Gu, J. M. Tranquada, Peter M. Gehring
The relationships among charge order, spin fluctuations, and superconductivity in underdoped cuprates remain controversial. We use neutron scattering techniques to study these phenomena in La1.93Sr0.07CuO4, a superconductor with a transition temperature of

Separation of Magnetic and Superconducting Behaviour in YBa 2 Cu 3 O 6.33 (T c =8.4 K)

April 29, 2015
Zahra Yamani, W.J. L. Buyers, F Wang, Young-June Kim, Jae-Ho Chung, Sung Chang, Peter M. Gehring, Goran Gasparovic, Christopher Stock, C. L. Broholm, J.C. Baglo, Ruixing Liang, D. A. Bonn, W. N. Hardy
Neutron scattering from high-quality YBa2Cu3O6.33 (YBCO6.33) single crystals with a Tc of 8.4 K shows no evidence of a coexistence of superconductivity with long-range antiferromagnetic order at this very low, near-critical doping of p~0.055. However, we

Neutron Inelastic Scattering Measurements of Low-Energy Phonons in the Multiferroic BiFeO 3

February 10, 2015
John A. Schneeloch, Zhijun Xu, Jinsheng Wen, Peter M. Gehring, Christopher Stock, M. Matsuda, B. Winn, Genda Gu, S. M. Shapiro, R. J. Birgeneau, T. Ushiyama, Y. Yanagisawa, Y. Tomioka, T. Ito, Guangyong Xu
We present neutron inelastic scattering measurements of the low-energy phonons in single crystal BiFeO3. The dispersions of the three acoustic phonon modes (LA along [100], TA1 along [010] and TA2 along [1¯10]) and two low energy optic phonon modes (LO and

Phase Diagram of the Relaxor Ferroelectric (1-x)Pb(Mg 1/3 Nb 2/3 )O 3-x PbTiO 3 Revisted: A neutron Powder Diffraction Study of the Relaxor Skin Effect

January 19, 2015
Daniel Phelan, Efrain E. Rodriguez, J Gao, Y Bing, Z.-G. Ye, Qingzhen Huang, Jinsheng Wen, Guangyong Xu, C. Stock, M Matsuura, Peter M. Gehring
We revisit the phase diagram of the relaxor ferroelectric PMN-xPT using neutron powder diffraction to test suggestions that residual oxygen vacancies and/or strain affect the ground state crystal structure. Powdered samples of PMN-xPT were prepared with

Fluctuating Defects in the Incipient Relaxor K 1-x Li x TaO 3 (x=0.02)

December 24, 2014
C. Stock, Peter M. Gehring, G. Xu, Daniel Lamago, Dmitry Reznik, M. Russina, Jinsheng Wen, Lynn A. Boatner
We report neutron scattering measurements of the structural correlations associated with the apparent relaxor transition in K1-xLixTaO2 for x=0.02 (KLT(0.02)). This compound displays a broad and frequency-dependent peak in the dielectric permittivity

Role of Random Electric Fields in Relaxors

February 14, 2014
Daniel P. Phelan, Christopher Stock, Jose A. Rodriguez, Songxue Chi, Juscelino B. Leao, Xifa Long, Yujuan Xie, Alexei A. Bokov, Zuo-Guang Ye, Panchapakesan Ganesh, Peter M. Gehring
Pb(Zr1¿xTix)O3 (PZT) and Pb[(Mg1/3Nb2/3)1¿xTix]O3 (PMN-xPT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudo-rhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are

Constraints on the Possible Long-Range Orbital Ordering in LaCoO 3

January 1, 2014
Daniel P. Phelan, Peter M. Gehring
A neutron powder diffraction measurement was performed to distinguish between the proposed monoclinic (I2/a) structure of LaCoO3, which is consistent with orbital ordering, and the rhombohedral (R3c) structure, which is inconsistent with orbital ordering

Lead-free and Lead-Based ABO 3 Perovskite Relaxors with Mixed-Valence A-Site and B-Site Disorder: A Comparative Neutron Scattering Structural Study of (NaYd1/2^Bi 1/2)TiO d3^ and Pb(MgYd1/3^Nb 2/3 )O 3

November 27, 2013
Wenwei Ge, Christopher P. Devreugd, Daniel Phelan, Qinhui Zhang, Muhtar Ahart, Jiefang Li, Haosu Luo, Lynn A. Boatner, Dwight Viehland, Peter M. Gehring
We report the results of neutron elastic scattering measurements between -250°C and 620°C on the lead-free relaxor Na1/2Bi1/2TiO3 (NBT). Strong, anisotropic, elastic diffuse scattering intensity decorates the (100), (110), (111), (200), (220), and (210)

Evidence for Anisotropic Polar Nanoregions in Relaxor Pb(Mg {1/3} Nb {2/3} )O 3 : A Neutron Study of the Elastic Constants and Anomalous TA Phonon Damping in PMN

September 18, 2012
Christopher K. Stock, Peter M. Gehring, H. Hiraka, I. Swainson, Guangyong Xu, Z.-G. Ye, J.-F. Li, D. Viehland
We use neutron inelastic scattering methods to characterize the acoustic phonons in the relaxor Pb(Mg{1/3}Nb{2/3})O3 (PMN) and demonstrate the presence of a highly anisotropic damping mechanism that is directly related to short-range, polar correlations

Single Crystal Study of Competing Rhombohedral and Monoclinic Order in Lead Zirconate Titanate

November 12, 2010
Daniel P. Phelan, X. Long, Y. Xie, Z.-G. Ye, A. M. Glazer, H. Yokota, P. A. Thomas, Peter M. Gehring
Neutron diffraction measurements were performed on single crystals of PbZr1¿xTixO3 (PZT)with x=0.325 and x=0.460. The data refute the thesis that the ferroelectric phases of PZT within this composition range, all of which are strongly piezoelectric, are