  Our Introduction starts with a short general review of the magnetic and
structural properties of the Heusler compounds which are under discussion in
this book. Then, more specifically, we come to the discussion of our
experimental results on multilayers composed of the Heusler alloys Co2MnGe and
Co2MnSn with V or Au as interlayers. The experimental methods we apply combine
magnetization and magneto-resistivity measurements, x-ray diffraction and
reflectivity, soft x-ray magnetic circular dichroism and spin polarized neutron
reflectivity. We find that below a critical thickness of the Heusler layers at
typically dcr = 1.5 nm the ferromagnetic order is lost and spin glass order
occurs instead. For very thin ferromagnetic Heusler layers there are
peculiarities in the magnetic order which are unusual when compared to
conventional ferromagnetic transition metal multilayer systems. In [Co2MnGe/Au]
multilayers there is an exchange bias shift at the ferromagnetic hysteresis
loops at low temperatures caused by spin glass ordering at the interface. In
[Co2MnGe/V] multilayers we observe an antiferromagnetic interlayer long range
ordering below a well defined Neel temperature originating from the dipolar
stray fields at the magnetically rough Heusler layer interfaces.
