155 research outputs found
Electric field control of multiferroic domains in NiVO imaged by X-ray polarization enhanced topography
The magnetic structure of multiferroic NiVO has been investigated
using non-resonant 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. New information on the magnetic structure in
the ferroelectric phase is obtained, where it is found that the magnetic
moments on the "cross-tie" sites are quenched relative to those on the "spine"
sites. 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.Comment: 9 pages, 6 figure
Circularly polarised X-rays as a probe of non-collinear magnetic order in multiferroic TbMnO3
Non-resonant X-ray magnetic scattering has been used to study the magnetic
structure of multiferroic TbMnO3 in its ferroelectric phase. Circularly
polarized X-rays were combined with a full polarization analysis of the
scattered beam to reveal important new information on the magnetic structure of
this canonical multiferroic. An applied electric field is shown to create a
magnetic nearly mono-domain state in which the cylcoidal order on the Mn
sublattice rotates either clockwise or counter-clockwise depending on the sign
of the field. It is demonstrated how this technique provides sensitivity to the
absolute sense of rotation of the Mn moments, and to components of the ordering
on the Tb sublattice and phase shifts that earlier neutron diffraction
experiments could not resolve.Comment: 4 pages, 3 figure
Resonant X-Ray Magnetic Scattering from CoO
We analyze the recent experiment [W. Neubeck {\em et al.}, Phys. Rev. B
\vol(60,1999,R9912)] for the resonant x-ray magnetic scattering (RXMS) around
the K edge of Co in the antiferromagnet CoO. We propose a mechanism of the RXMS
to make the states couple to the magnetic order: the intraatomic exchange
interaction between the and the states and the - mixing to the
states of neighboring Co atoms. These couplings induce the orbital moment
in the states and make the scattering tensor antisymmetric. Using a
cluster model, we demonstrate that this modification gives rise to a large RXMS
intensity in the dipole process, in good agreement with the experiment. We also
find that the pre-edge peak is generated by the transition to the states
in the quadrupole process, with negligible contribution of the dipole process.
We also discuss the azimuthal angle dependence of the intensity.Comment: 15 pages, 8 figure
Femtoscale magnetically induced lattice distortions in multiferroic TbMnO3
Magneto-electric multiferroics exemplified by TbMnO3 possess both magnetic
and ferroelectric long-range order. The magnetic order is mostly understood,
whereas the nature of the ferroelectricity has remained more elusive. Competing
models proposed to explain the ferroelectricity are associated respectively
with charge transfer and ionic displacements. Exploiting the magneto-electric
coupling, we use an electric field to produce a single magnetic domain state,
and a magnetic field to induce ionic displacements. Under these conditions,
interference charge-magnetic X-ray scattering arises, encoding the amplitude
and phase of the displacements. When combined with a theoretical analysis, our
data allow us to resolve the ionic displacements at the femtoscale, and show
that such displacements make a significant contribution to the zero-field
ferroelectric moment.Comment: This is the author's version of the work. It is posted here by
permission of the AAAS for personal use, not for redistribution. The
definitive version was published in Science VOL 333, (2011),
doi:10.1126/science.120808
Profile of the U 5f magnetization in U/Fe multilayers
Recent calculations, concerning the magnetism of uranium in the U/Fe
multilayer system have described the spatial dependence of the 5f polarization
that might be expected. We have used the x-ray resonant magnetic reflectivity
technique to obtain the profile of the induced uranium magnetic moment for
selected U/Fe multilayer samples. This study extends the use of x-ray magnetic
scattering for induced moment systems to the 5f actinide metals. The spatial
dependence of the U magnetization shows that the predominant fraction of the
polarization is present at the interfacial boundaries, decaying rapidly towards
the center of the uranium layer, in good agreement with predictions.Comment: 7 pages, 6 figure
Observation Of Orbital Moment In Nio Using Magnetic X-ray Scattering
The spin and orbital contribution to the total magnetization have been measured in NiO by exploiting the polarization dependence of nonresonant x-ray magnetic scattering. Although the orbital moment is usually neglected, we observed that the orbital moment actually plays an important role with a contribution of 17% to the total magnetization density. By performing azimuthal scans, it was found that spin and orbital moments are collinear. © 1999 American Institute of Physics.858 II A48474849Muraki, Y., (1998) Phys. Rev. Lett., 81, p. 582Muraki, Y., (1998) Phys. Rev. Lett., 80, p. 1932Blume, M., Gibbs, D., (1988) Phys. Rev. B, 37, p. 1779Shull, C.G., Strauser, W.A., Wollan, F.O., (1951) Phys. Rev., 83, p. 333Baruchel, J., Schlenker, M., Kuusowa, K., Saito, S., (1981) Philos. Mag. B, 43, p. 853Roth, W., (1960) J. Appl. Phys., 31, p. 2000Bergevin, F.D., Brunel, M., (1972) Phys. Lett., 39 A2, p. 141Brunel, M., Bergevin, F.D., (1981) Acta Crystallogr. A, 37, p. 324Blume, M., (1985) J. Appl. Phys., 57, p. 3615Alperin, H.A., (1962) J. Phys. Soc. Jpn., 17 B-III, p. 12Stunault, A., (1998) J. Synchrotron Radiat., 5, p. 1010Fernandez, V., (1998) Phys. Rev. B, 57, p. 7870Blume, M., (1961) Phys. Rev., 124, p. 9
Circularly Polarized X Rays as a Probe of Noncollinear Magnetic Order in Multiferroic TbMnO3 (vol 102, 237205, 2009)
Erratum: Circularly Polarized X Rays as a Probe of Noncollinear Magnetic Order in Multiferroic TbMnO3 [Phys. Rev. Lett. 102, 237205 (2009)
Mechanism of resonant x-ray magnetic scattering in NiO
We study the resonant x-ray magnetic scattering (RXMS) around the K edge of
Ni in the antiferromagnet NiO, by treating the 4p states of Ni as a band and
the 3d states as localized states. We propose a mechanism that the 4p states
are coupled to the magnetic order through the intra-atomic Coulomb interaction
between the 4p and the 3d states and through the p-d mixing to the 3d states of
neighboring Ni atoms. These couplings induce the orbital moment in the 4p band,
and thereby give rise to the RXMS intensity at the K edge in the dipolar
process. It is found that the spin-orbit interaction in the 4p band has
negligibly small contribution to the RXMS intensity. The present model
reproduces well the experimental spectra. We also discuss the azimuthal angle
dependence of the intensity.Comment: 10 pages (revtex) and 7 postscript figure
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