Imaging and characterization of conducting ferroelectric domain walls by photoemission electron microscopy

Schaab, Jakob; Krug, I.; Nickel, F.; Gottlob, Daniel M.; Doğanay, Hatice; Cano, A.; Hentschel, Mario; Yan, Z.; Bourret, Edith; Schneider, Claus M.; Ramesh, R.; Meier, Dennis

doi:10.1063/1.4879260

Cited by 30 publications

(30 citation statements)

References 39 publications

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“…Thus, while the detected conductance variations of about one decade [4] or a factor of 4 [16] in ErMnO3 and of 25% in HoMnO3 [8] provide strong indications for different conductivities of domains and walls, no unequivocal information on the absolute value of the conductivity contrast is gathered. Recent photoemission electronmicroscopy experiments on ErMnO3 have demonstrated the intrinsic nature of the conductivity variation between domains and DWs [17] but this technique also does not provide absolute values. These are fundamental problems that go beyond hexagonal manganites and also apply to functional ferroelectric domain walls in other systems.…”

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confidence: 99%

Conductivity Contrast and Tunneling Charge Transport in the Vortexlike Ferroelectric Domain Patterns of Multiferroic Hexagonal YMnO3

et al. 2017

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We deduce the intrinsic conductivity properties of the ferroelectric domain walls around the topologically protected domain vortex cores in multiferroic YMnO3. This is achieved by performing a careful equivalent-circuit analysis of dielectric spectra measured in single-crystalline samples with different vortex densities. The conductivity contrast between the bulk domains and the less conducting domain boundaries is revealed to reach up to a factor 500 at room temperature, depending on sample preparation. Tunneling of localized defect charge carriers is the dominant charge-transport process in the domain walls that are depleted of mobile charge carriers. This work demonstrates that via equivalent-circuit analysis, dielectric spectroscopy can provide valuable information on the intrinsic charge-transport properties of ferroelectric domain walls, which is of high relevance for the design of new domain-wall-based microelectronic devices.The hexagonal manganites RMnO3 (R = Sc, Y, In, and Dy-Lu) form a unique group of multiferroics where a geometrically-driven mechanism triggers improper ferroelectricity [1]. Additional interest in this material class arose from the reported occurrence of vortex-like ferroelectric domain patterns [2,3,4]. Around the vortex cores, forming the centers of "cloverleaf" patterns of six domains, the polarization changes sign six times. These cores, evolving at a high-temperature structural transition [5], represent stable topological defects. Even strong electric fields only lead to a variation of ferroelectric domain sizes in these materials, but are unable to completely eradicate unfavorable domains and to generate a mono-domain state [2,6]. Moreover, there is a strict coupling of ferroelectric and antiferromagnetic domain walls (DWs), the latter forming at much lower temperatures around 100 K [7].Recently it was shown that these complex domain properties also may be of relevance from an application point of view: Conductive atomic-force microscopy (c-AFM) on ErMnO3 [4] and HoMnO3 [8] revealed that the conductance of the ferroelectric DWs is either enhanced or suppressed compared to the domains, being determined by the polarization orientation of the adjacent domains. As the DWs can be easily tuned by external fields, this opens the possibility of domain-boundary engineering and applications in microelectronics using the nanoscale DWs instead of the domains themselves as active device elements [9,10,11,12,13]. The hexagonal manganites seem especially suited for this kind of functionality: Their DWs are robust and represent persistent interfaces as they are attached to the vortex cores, but within these constraints they can be moved by an external field thus enabling switching [4,12,13].In general, insulating domain walls, also observed in various other systems as SrMnO3 thin films [14] and (Ca,Sr)3Ti2O7 [15], have shifted into the focus of interest, due to their possible applications, e.g., as rewritable nanocapacitors. The conductivity contrast between these DWs and the domains should be...

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Conductivity Contrast and Tunneling Charge Transport in the Vortexlike Ferroelectric Domain Patterns of Multiferroic Hexagonal YMnO3

et al. 2017

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“…The key to discover or design multiferroic materials is a fundamental understanding of the microscopic coupling mechanisms, particularly, the behavior of the underlying domain structures, the role of spinorbit coupling, and the nanoscale confinement. Soft X-ray microscopies are therefore ideally suited to investigate such materials [206], [207].…”

Section: B Magnetic Dwsmentioning

confidence: 99%

X-Ray Imaging of Magnetic Structures

Fischer

2015

IEEE Trans. Magn.

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The characterization of nanoscale magnetic structures, their static properties, and fast spin dynamics with polarized soft X-rays has become an indispensable analytical tool due to the unique features of those probes. The spectroscopic magnetic response serves as a fingerprint of the specimen and can give quantitative information on element-specific spin and orbital magnetic moments. Images of magnetic domain structures at a spatial resolution down to nearly 10 nm, ultimately in all three dimensions, can be obtained with various X-ray microscopy techniques and can further be combined with stroboscopic pump-probe schemes to image the spin dynamics of spin structures, such as the motion of domain walls in nanowires or the vortex core dynamics in micropatterned magnetic elements. Next generation sources of polarized soft X-rays such as X-ray free electron lasers or high-harmonic generation laser sources hold the promise to provide nanometer spatial and femtosecond time resolution, enabling to address thus fundamental magnetic length and time scales in magnetism. This paper reviews the various X-ray imaging techniques using polarized soft X-rays by summarizing their characteristic features, recent achievements, and current limitations as well as future opportunities. A brief overview on other magnetic imaging techniques are given to set magnetic X-ray imaging techniques into context. Index Terms-Magnetic diffractive imaging, photoemission electron microscopy, soft X-ray spectromicroscopy, spin dynamics, X-ray magnetic circular dichroism (XMCD), X-ray optics. 0018-9464

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“…The DC conduction current (j c ) measurements were made usually using macroscopic electrodes [5,12,15] and conductive tip of the atomic force microscope [7,13,16]. Some sophisticated techniques like Xray photoemission electron microscopy (XPEEM) and scanning nonlinear dielectric microscopy (SNDM) were also used [14,17].…”

Section: Introductionmentioning

confidence: 99%

Increase and Relaxation of Abnormal Conduction Current in Lithium Niobate Crystals with Charged Domain Walls

et al. 2015

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The increase and relaxation of the conduction current caused by formation of intergrown charged domain walls (CDW) during polarization reversal have been studied in stoichiometric lithium niobate. The 10 3 -10 4 times increase of the conduction current was revealed in the temperature range 100-200 C. The current, measured during polarization reversal, consists of the conventional switching current and the conduction current along CDW dominating for T>200 C. The model based on the complex conductivity pathway along CDW was proposed. The current data were analyzed in terms of the Kolmogorov-Avrami model taking into account the input of the CDW conductivity.

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Imaging and characterization of conducting ferroelectric domain walls by photoemission electron microscopy

Abstract: High-resolution X-ray photoemission electron microscopy (X-PEEM) is a well

Cited by 30 publications

References 39 publications

Conductivity Contrast and Tunneling Charge Transport in the Vortexlike Ferroelectric Domain Patterns of Multiferroic Hexagonal YMnO3

Conductivity Contrast and Tunneling Charge Transport in the Vortexlike Ferroelectric Domain Patterns of Multiferroic Hexagonal YMnO3

X-Ray Imaging of Magnetic Structures

Increase and Relaxation of Abnormal Conduction Current in Lithium Niobate Crystals with Charged Domain Walls

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