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Abstract:
The Heusler compound Co2FeSi is a promising material for
magneto-electronic devices. With a Curie temperature of 1100K and a
saturation magnetization of 6 Bohr magnetons and a high spin
polarization at the Fermi edge it fulfils the essential requirements for
magnetic sensors or spin valve structures. An essential feature for such
devices is the micro-magnetic domain structure. X-ray magnetic circular
dichroism - photo emission electron microscopy has been used for a
direct observation of the domain structure of single- and
polycrystalline samples. The polycrystalline material exhibits a
micro-magnetic ripple structure, as it is well known for pure Co and
other polycrystalline Heusler compounds. The ( 1 1 0)- oriented surface
of the single crystal exhibits a multi-domain pattern characteristic for
systems with an easy axis that might point out of the surface.
Asymmetric 180. Bloch walls with changing sense of rotation are observed
between oppositely magnetized domains. Spin polarized photo emission
from a single domain of the single crystal shows a spin polarization of
16% at the Fermi energy and up to 35% in the d-bands, at room
temperature.
