Seminars Archive
Soft x-ray resonant magnetic scattering from magnetic nanostructures
Abstract
Wednesday, March 27, 2002, 15:00
Seminar Room, Building "T"
Sincrotrone Trieste, Basovizza
Soft x-ray resonant magnetic scattering from magnetic nanostructures
Gerrit van der Laan
( Daresbury Laboratory, Warrington WA4 4AD, UK)
ABSTRACT
Regular magnetic domain patterns are a characteristic feature of many
low-dimensional systems with phases
stabilized by competing interactions. In ultrathin magnetic films such
a domain structure can occur when the spin
moments prefer to order perpendicular to the film plane. These systems
are of particular interest for magneto-optical
storage devices and display the giant magneto-resistance effect utilized
in magnetic field sensors. It is the
competition between perpendicular magnetocrystalline anisotropy (PMA)
and dipolar spin-spin magnetic interaction
that leads to the regular domain pattern.
We present the novel method of circular dichroism in soft x-ray resonant
magnetic scattering (XRMS) that can be used
for depth profiling of these materials. [1,2] We utilize the strong
magneto-optical effect at the L2,3 absorption edges
of 3d transition metals that causes a Faraday rotation of the (linearly)
polarized x-rays analogous to, but much
stronger than, the Kerr ellipticity in the visible region. The circular
polarization allows us to observe correlations
between the perpendicular domains and adjacent closure regions. The
interference observed between scattering
channels is a direct tool to study closure domains and domain walls.
[3] Application to single crystalline FePd
layers allows to monitor magnetic flux closure domains. It was found
that flux closure occurs in samples with low to
medium PMA, while a high PMA impedes closure domain formation. [4]
We further used XRMS to study arrays of silicon lines covered by a
Co/Pt multilayer. The magnetic signal appearing
at the Co L3 resonance reveals an antiferromagnetic order at the demagnetized
state. We studied the influence of the
magnetic history on the magnetic peaks and observed an increase for
particular demagnetization processes. XRMS can
be used to monitor the magnetization reversal, showing how the antiferromagnetic
order (dis)appears near the coercive
field. Also some magnetic speckle results will be presented.
[1] G. van der Laan et al., Physica B 283, 171 (2000).
[2] G. van der Laan, Synchr. Rad. News, 12 (3) 5 (1999);
ibid 14 (5), 32 (2001).
[3] H.A. Durr et al., Science 284, 2166 (1999).
[4] E. Dudzik et al., Phys. Rev. B 62, 5779 (2000).
