A spatially resolved investigation of the local, micro-magnetic domain structure of single and polycrystalline Co2FeSi

Abstract

The Heusler compound Co2FeSi is a promising material for magneto-electronic devices. With a Curie temperature of 1100 K 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.