  Interface magnetism and topological structure of Fe on organic semiconductor
film (Alq3) have been studied and compared with Fe film deposited directly on
Si (100) substrate. To get information on the diffused Fe layer at the Fe/Alq3
interface, grazing incident nuclear resonance scattering (GINRS) measurements
are made depth selective by introducing a 95% enriched thin 57Fe layer at the
Interface and producing x-ray standing wave within the layered structure.
Compared with Fe growth on Si substrate, where film exhibits a hyperfine field
value of 32 T (Bulk Fe), a thick Fe- Alq3 interface has been found with reduced
electron density and hyperfine fields providing evidence of deep penetration of
Fe atoms into Alq3 film. Due to the soft nature of Alq3, Fe moments relax in
the film plane. At the same time, Fe on Si has a resultant ~43 deg out-of-plane
orientation of Fe moments at the Interface due to the stressed and rough Fe
layer near Si. The evolution of magnetism at the Fe-Alq3 Interface is monitored
using in-situ magneto-optical Kerr effect (MOKE) during the growth of Fe on the
Alq3 surface and small-angle x-ray scattering (SAXS) measurements. It is found
that the Fe atom tries to organize into clusters to minimize their
surface/interface energy. The origin of the 2.4 nm thick magnetic dead layer at
the Interface is attributed to the small Fe clusters of paramagnetic or
superparamagnetic nature. The present work provides an understanding of
interfacial magnetism at metal-organic interfaces and the topological study
using the GI-NRS technique, which is made depth selective to probe magnetism of
the diffused ferromagnetic layer, which is otherwise difficult for lab-based
techniques.
