Electric field control of multiferroic domains in ${\text{Ni}}_{3}{\text{V}}_{2}{\text{O}}_{8}$ imaged by x-ray polarization-enhanced topography

Electric field control of multiferroic domains in ${Ni}_{3} V_{2} O_{8}$ imaged by x-ray polarization-enhanced topography

F. Fabrizi, H. C. Walker, L. Paolasini, F. de Bergevin, T. Fennell, N. Rogado, R. J. Cava, Th. Wolf, M. Kenzelmann, and D. F. McMorrow

Phys. Rev. B 82, 024434 – Published 30 July 2010

Abstract

The magnetic structure of multiferroic ${Ni}_{3} V_{2} O_{8}$ has been investigated using nonresonant x-ray magnetic scattering. Incident circularly polarized x rays combined with full polarization analysis of the scattered beam is shown to yield high sensitivity to the components of the cycloidal magnetic order, including their relative phases. Information on the magnetic structure in the ferroelectric phase is obtained, where it is found that the magnetic moments on the “cross-tie” sites remain disordered. This implies that the onset of ferroelectricity is associated mainly with spine site magnetic order. We also demonstrate that our technique enables the imaging of multiferroic domains through polarization enhanced topography. This approach is used to image the domains as the sample is cycled by an electric field through its hysteresis loop, revealing the gradual switching of domains without nucleation.

Received 23 April 2010

DOI:https://doi.org/10.1103/PhysRevB.82.024434

Authors & Affiliations

F. Fabrizi^1,2, H. C. Walker^1,2, L. Paolasini¹, F. de Bergevin¹, T. Fennell^2,3, N. Rogado⁴, R. J. Cava⁴, Th. Wolf⁵, M. Kenzelmann⁶, and D. F. McMorrow²

¹European Synchrotron Radiation Facility, Boîte Postale 220, 38043 Grenoble, France
²London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
³Institut Laue-Langevin, 38042 Grenoble, France
⁴Department of Chemistry and Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544, USA
⁵Institut für Festkörperphysik, Karlsruher Institut für Technologie, D-76021 Karlsruhe, Germany
⁶Laboratory for Developments and Methods, Paul Scherrer Institute, CH-5232 Villigen, Switzerland

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Vol. 82, Iss. 2 — 1 July 2010

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Figure 1
(Color online) Crystallographic and LTI magnetic structure of the nickel sublattice in ${Ni}_{3} V_{2} O_{8}$ . (a) Schematic of the two nickel sites: spine (gray or red online) and cross-tie (black) (b) Projection onto the $a − b$ plane of the proposed LTI magnetic structure of the spine sites $m^{S P} = (1.6 \pm 0.1, 1.3 \pm 0.1, 0) μ_{B}$ and the cross-tie sites $m^{C T} = (2.2 \pm 0.1, 1.4 \pm 0.1, 0) μ_{B}$ , as deduced from neutron-diffraction measurements (Ref. 28).Reuse & Permissions
Figure 2
(Color online) Schematic of the experimental setup, where for a given magnetic satellite the Stokes parameters are determined by measuring the scattered intensity as a function of the angle $η$ .Reuse & Permissions
Figure 3
(Color online) Temperature dependence of the scattering intensity (upper) and wave-vector position (lower panel) of the magnetic satellite $(5 - τ, 1, 0)$ measured in the $π − σ^{'}$ channel. The lines (Ref. 28) define the boundaries of the low-temperature incommensurate phase of interest. The inset in the top panel shows a typical reciprocal space scan along the $h$ direction of the same satellite, measured at $T = 4 K$ .Reuse & Permissions
Figure 4
(Color online) The Stokes dependence of the scattered intensity from magnetic satellites on analyzer rotation angle $η$ was determined by the data measured in the LTI phase with LCP and RCP x rays after field cooling with $E = 1 kV / mm$ along $- b$ . The solid lines represent calculations with spin moments of $m_{a}^{S P} = 1.6$ , $m_{b}^{S P} = 1.3$ , $m_{a}^{C T} = 0$ , and $m_{b}^{C T} = 0$ , in units of $μ_{B}$ , and a domain population of 87%. The dashed lines correspond to the neutron model (Ref. 28) with finite cross-tie moments [Fig. 1b], with an assumed phase difference of $π / 2$ between the spine and cross-tie moments, and where the intensities are scaled to that of the upper panel.Reuse & Permissions
Figure 5
(Color online) (a) Image of the sample sandwiched between the Cu electrodes used to form a capacitor. The dotted mesh superimposed on the image indicates points at which the domain population was determined. The ellipse indicates the size of the x-ray beam. (b) Variation in the Stokes parameters as a function of domain volume fraction, demonstrating the sensitivity to $P_{2}$ (blue line) and insensitivity to $P_{1}$ (red line), allowing a contrast to be measured between the two cycloidal domains. (c) Images of the domain populations as a function of applied electric field for the magnetic reflection $(5 + τ, 1, 0)$ , where the color represents the percentage of the clockwise and anticlockwise magnetic cycloidal domains.Reuse & Permissions
Figure 6
(Color online) Position-dependent magnetic domain population hysteresis loops obtained from the domain images shown in Fig. 5 averaged over different areas of interest: (a) entire sample area; (b) edge; and (c) central region. In (c) the data are compared with bulk measurements of the electric polarization (Ref. 31) where an appropriate scaling has been applied.Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Electric field control of multiferroic domains in ${Ni}_{3} V_{2} O_{8}$ imaged by x-ray polarization-enhanced topography

F. Fabrizi, H. C. Walker, L. Paolasini, F. de Bergevin, T. Fennell, N. Rogado, R. J. Cava, Th. Wolf, M. Kenzelmann, and D. F. McMorrow

Phys. Rev. B 82, 024434 – Published 30 July 2010

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Physical Review B

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Electric field control of multiferroic domains in Ni3V2O8 imaged by x-ray polarization-enhanced topography

F. Fabrizi, H. C. Walker, L. Paolasini, F. de Bergevin, T. Fennell, N. Rogado, R. J. Cava, Th. Wolf, M. Kenzelmann, and D. F. McMorrow

Phys. Rev. B 82, 024434 – Published 30 July 2010

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Electric field control of multiferroic domains in ${Ni}_{3} V_{2} O_{8}$ imaged by x-ray polarization-enhanced topography