International Workshop on Processing and Characterization of Nanomaterials 

Formation and Transformation of Antiferromagnetic Domains in Metallic 
Multilayers: the Reflectometric Approach 

Dénes Lajos Nagy, László Bottyán, László Deák, Márton Major, Edit Szilágyi 
KFKI Research Institute for Particle and Nuclear Physics P.O.B. 49, 
H 1525 Budapest, Hungary 
nagy@rmki.kfki.hu, bottyan@rmki.kfki.hu, deak@rmki.kfki.hu, 
major@rmki.kfki.hu, szilagyi@rmki.kfki.hu 

Abstract The magnetocrystalline anisotropy in antiferromagnetically (AF)
coupled metallic multilayers may lead to spectacular effects, which can be
most efficiently studied by two closely related nuclear scattering
techniques, namely synchrotron Mössbauer reflectometry (SMR) and polarised
neutron reflectometry (PNR). A spin-flop transition takes place in a
strongly AF-coupled epitaxial Fe/Cr multilayer of fourfold in-plane
anisotropy when a moderate magnetic field is applied along the easy axis
in which the layer magnetisations actually lay. The electronically
forbidden AF reflections in a specular SMR experiment fully appear or
completely disappear dur-ing the spin-flop transition. In case of specular
PNR, the AF reflection moves from the spin-flip to the non-spin-flip
channel on spin-flop transition or vice versa. The off-specular SMR and
PNR techniques are sensitive to the in-plane correlation length x of the
layer magnetisation direction and are, thereby, able to map the size
distribu-tion of the AF domains in multilayers. A dramatic increase of x
from about 1 mm to at least 10 mm, i.e., a coarsening of the AF domains
was observed in the same multilayer when it passed the spin-flop
transition pro-vided that the external magnetic field was previously
decreased from magnetic saturation to zero. This shows the key role of the
in-plane magnetocrystalline anisotropy in the domain-coarsening process.
Finally we demon-strate how the formation of sub-micrometer domains can be
followed by SMR and PNR.

Key Words: Multilayers, antiferromagnetic coupling, domains, nuclear
resonant scattering of synchrotron radiation, synchrotron Mössbauer
reflectometry, polarised neutron reflectometry