Browsing by Author "Seidel, Jan"

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A nanoscale shape memory oxide
(2013-11-01)
Zhang, Jinxing
;
Ke, Xiaoxing
;
Gou, Gaoyang
;
Seidel, Jan
;
Xiang, Bin
Stimulus-responsive shape-memory materials have attracted tremendous research interests recently, with much effort focused on improving their mechanical actuation. Driven by the needs of nanoelectromechanical devices, materials with large mechanical strain, particularly at nanoscale level, are therefore desired. Here we report on the discovery of a large shape-memory effect in bismuth ferrite at the nanoscale. A maximum strain of up to similar to 14% and a large volumetric work density of similar to 600 +/- 90 J cm(-3) can be achieved in association with a martensitic-like phase transformation. With a single step, control of the phase transformation by thermal activation or electric field has been reversibly achieved without the assistance of external recovery stress. Although aspects such as hysteresis, microcracking and so on have to be taken into consideration for real devices, the large shape-memory effect in this oxide surpasses most alloys and, therefore, demonstrates itself as an extraordinary material for potential use in state-of-art nanosystems.
Atomic-Scale Evolution of Local Electronic Structure Across Multiferroic Domain Walls
(2011-04-05)
Chiu, Ya-Ping
;
Chen, Yu-Ting
;
Huang, Bo-Chao
;
Shih, Min-Chuan
;
Yang, Jan-Chi
Direct evidence of the electronic configurations across domain walls in BiFeO(3) is quantitatively characterized by cross-sectional scanning tunneling microscopy. Atomic-scale band evolution and the asymmetrically built-in potential barrier at domain boundaries are demonstrated. The 109 degrees domain walls register a remarkable decrease in the bandgap, suggesting a new route to control the local conducting channels within 2 nm.
Concurrent transition of ferroelectric and magnetic ordering near room temperature
(2011-11-01)
Ko, Kyung-Tae
;
Jung, Min Hwa
;
He, Qing
;
Lee, Jin Hong
;
Woo, Chang Su
Strong spin-lattice coupling in condensed matter gives rise to intriguing physical phenomena such as colossal magnetoresistance and giant magnetoelectric effects. The phenomenological hallmark of such a strong spin-lattice coupling is the manifestation of a large anomaly in the crystal structure at the magnetic transition temperature. Here we report that the magnetic Neel temperature of the multiferroic compound BiFeO3 is suppressed to around room temperature by heteroepitaxial misfit strain. Remarkably, the ferroelectric state undergoes a first-order transition to another ferroelectric state simultaneously with the magnetic transition temperature. Our findings provide a unique example of a concurrent magnetic and ferroelectric transition at the same temperature among proper ferroelectrics, taking a step toward room temperature magnetoelectric applications.
Directed assembly of nano-scale phase variants in highly strained BiFeO3 thin films
(2012-09-15)
Zhou, Jian
;
Trassin, Morgan
;
He, Qing
;
Tamura, Nobumichi
;
Kunz, Martin
The delicate balance between elastic energy and electrostatic energy in highly strained BiFeO3 (BFO) thin films results in complex mixed-phase patterns, which poses significant challenges for theoretical understanding and complicates the realization of its full potential in magnetoelectric, electromechanical, and photovoltaic devices. In this letter, we explore in-plane electric field induced phase transition in strain engineered BFO thin films and elucidate the mechanism behind the assembly behavior of complex nano-scale phase domains. Our approach enables deterministic control of phase variants with well-defined structures and orientation, paving the way for designing novel data storage devices based on mixed phase BFO. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752395]
Domain wall functionality in BiFeO3
(2013)
Seidel, Jan
;
Singh-Bhalla, Guneeta
;
He, Qing
;
Yang, Seung-Yeul
;
Chu, Ying-Hao
In this article we provide an overview of phenomena involving domain walls in BiFeO3 as nanoscale functional elements. Because ferroelectric domain walls can be routinely modified using electric fields, our results suggest a new degree of flexibility for domain boundary engineering and oxide-based nanoelectronics.
Dynamic Conductivity of Ferroelectric Domain Walls in BiFeO(3)
(2011-05-01)
Maksymovych, Peter
;
Seidel, Jan
;
Chu, Ying Hao
;
Wu, Pingping
;
Baddorf, Arthur P.
Topological walls separating domains of continuous polarization, magnetization, and strain in ferroic materials hold promise of novel electronic properties, that are intrinsically localized on the nanoscale and that can be patterned on demand without change of material volume or elemental composition. We have revealed that ferroelectric domain walls in multiferroic BiFeO(3) are inherently dynamic electronic conductors, closely mimicking memristive behavior and contrary to the usual assumption of rigid conductivity. Applied electric field can cause a localized transition between insulating and conducting domain walls, tune domain wall conductance by over an order of magnitude, and create a quasicontinuous spectrum of metastable conductance states. Our measurements identified that subtle and microscopically reversible distortion of the polarization structure at the domain wall is at the origin of the dynamic conductivity. The latter is therefore likely to be a universal property of topological defects in ferroelectric semiconductors.
Dynamic Conductivity of Ferroelectric Domain Walls in BiFeO3
(2011-05-01)
Maksymovych, Peter
;
Seidel, Jan
;
Chu, Ying Hao
;
Wu, Pingping
;
Baddorf, Arthur P.
Topological walls separating domains of continuous polarization, magnetization, and strain in ferroic materials hold promise of novel electronic properties, that are intrinsically localized on the nanoscale and that can be patterned on demand without change of material volume or elemental composition. We have revealed that ferroelectric domain walls in multiferroic BiFeO3 are inherently dynamic electronic conductors, closely mimicking memristive behavior and contrary to the usual assumption of rigid conductivity. Applied electric field can cause a localized transition between insulating and conducting domain walls, tune domain wall conductance by over an order of magnitude, and create a quasicontinuous spectrum of metastable conductance states. Our measurements identified that subtle and microscopically reversible distortion of the polarization structure at the domain wall is at the origin of the dynamic conductivity. The latter is therefore likely to be a universal property of topological defects in ferroelectric semiconductors.
Magnetic and Magnetodielectric Properties of Epitaxial Iron Vanadate Thin Films
(2017-01)
Zhou, Dongyi
;
Takahashi, Ryota
;
Zhou, Yanyu
;
Kim, Dohyung
;
Suresh, Vandrangi Kumar
The magnetic and magnetodielectric behavior of epitaxial (001) transition metal oxide spinel iron vanadate (Fe1+xV2-xO4, FVO) thin films grown on (001) SrTiO3 substrates by pulsed laser deposition is reported. X-ray absorption spectroscopy studies confirm the trivalent and nominally divalent nature of V and Fe ions, respectively, while an excess of Fe3+ ions is also found. Aberration-corrected cross-sectional scanning transmission electron microscopy analysis suggests that the excess Fe3+ may be accommodated through Fe3O4 stacking faults along the {111} planes. Temperature-dependent X-ray magnetic circular dichroism spectra reveal an anti-parallel alignment of spins between the Fe2+ and V3+ cations. M-H loops acquired at 10 K, well below the noncollinear ferromagnetic phase transition temperature, show magnetic anisotropy and point to the existence of two distinct phases with different coercive fields. Visual evidence for magnetic domains and their switching is given by magnetic force microscopy, which finds a switching field of approximate to 3 T in agreement with the M-H loops. Magnetodielectric measurements for a Pd/FVO/Nb:STO heterostructure reveal a weak hysteresis in the magneto-capacitance loops at 10 K, thus confirming magneto-dielectric coupling. Detailed temperature and frequency-dependent dielectric studies find that Maxwell-Wagner-type relaxation dominates capacitance behavior above approximate to 40 K due to a FVO/Nb:SrTiO3 Schottky interface.
Magnetic and Magnetodielectric Properties of Epitaxial Iron Vanadate Thin Films
(2017-01)
Zhou, Dongyi
;
Takahashi, Ryota
;
Zhou, Yanyu
;
Kim, Dohyung
;
Suresh, Vandrangi Kumar
The magnetic and magnetodielectric behavior of epitaxial (001) transition metal oxide spinel iron vanadate (Fe1+xV2-xO4, FVO) thin films grown on (001) SrTiO3 substrates by pulsed laser deposition is reported. X-ray absorption spectroscopy studies confirm the trivalent and nominally divalent nature of V and Fe ions, respectively, while an excess of Fe3+ ions is also found. Aberration-corrected cross-sectional scanning transmission electron microscopy analysis suggests that the excess Fe3+ may be accommodated through Fe3O4 stacking faults along the {111} planes. Temperature-dependent X-ray magnetic circular dichroism spectra reveal an anti-parallel alignment of spins between the Fe2+ and V3+ cations. M-H loops acquired at 10 K, well below the noncollinear ferromagnetic phase transition temperature, show magnetic anisotropy and point to the existence of two distinct phases with different coercive fields. Visual evidence for magnetic domains and their switching is given by magnetic force microscopy, which finds a switching field of approximate to 3 T in agreement with the M-H loops. Magnetodielectric measurements for a Pd/FVO/Nb:STO heterostructure reveal a weak hysteresis in the magneto-capacitance loops at 10 K, thus confirming magneto-dielectric coupling. Detailed temperature and frequency-dependent dielectric studies find that Maxwell-Wagner-type relaxation dominates capacitance behavior above approximate to 40 K due to a FVO/Nb:SrTiO3 Schottky interface.