Surface diffraction on magnetic nanostructures in thin films using grazing incidence SANS. M. Pannetier (a), F. Ott (b), C. Fermon (b), Y. Samson (c) (a) DRECAM/SPEC, CEA Saclay, Gif sur Yvette FRANCE (b) Lab. Léon Brillouin CEA/CNRS, Gif sur Yvette FRANCE (c) CEA Grenoble DRFMC/SP2M, 17 rue des Martyrs Grenoble France

Outline Principle of the experiment Scattering on a FePd system Data simulations Other prospective systems

Principle of the experiment Under total reflection angle ( c ) an evanescent wave is travelling parallel to the surface penetration depth nm i < c kiki kfkf

Scattering geometry z xy neutrons Incidence plane < Q y < nm nm < < 60 µm incidence plane < Q y < 3 nm nm < < 100 nm

Experimental set-up Spectrometer PAPOL at the LLB Saclay sample slit 1H Specular reflected beam Incidence angle on the sample i slit 2H diffracted beam polariser Detector Y X Z

FePd layers Fe 0.5 Pd 0.5 alloy layers self- organise in magnetic stripes Domain sizes :60 nm Wall thickness :6 nm Magnetic domains Field B = Hd + M Simulation OOMMF DRFMC CEA Grenoble

Magnetic sensitivity Top view kiki kfkf qyqy The domains magnetisation contribute to the scattering Neel caps do not contribute Bloch wall do contribute Néel cap Mup Mdo

M and B components in the layer MBMB X Y Z

GID scattering on the PSD c = 0.7° Beam stop diffraction Specular line Refracted signal Qy Qz

Calcul plus complet (facteur de forme inclus) Sin(PhiF) vs Sin(Theta out) ; Theta In = 0.2° (stupide) Gauche ligne sur substrat; droite vraie situation (sauf épaisseur) Les échelles de couleurs ne corespondne tpas du tout au meme intensités!!!

Problem of the stray fields The stray fields are not negligible – They create a rather large magnetic potential outside the layer

GID 2D grating (top view) TF Rods 2 /d d Ewald sphere kiki kfkf kiki

Other example : Co clusters in Al 2 O 3 Co/Al2O3 D.Babonneau et al, APL 76 (2000) 2 / 5.4nm GISANS Correlation fonction Form factor