ISSN 1063-7834, Physics of the Solid State, 2014, Vol. 56, No. 3, pp. 505–510. © Pleiades Publishing, Ltd., 2014. Original Russian Text © I.D. Lobov, M.M. Kirillova, A.A. Makhnev, L.N. Romashev, M.A. Milyaev, V.V. Ustinov, 2014, published in Fizika Tverdogo Tela, 2014, Vol. 56, No. 3, pp. 492–497. 505 1. INTRODUCTION The existence of the giant magnetoresistance (GMR) in magnetic multilayer nanostructures is explained by asymmetry of the spin-dependent scat- tering of conduction electrons at interfaces and in bulk of the ferromagnetic layers. The theoretical estima- tions of the spin asymmetry coefficient of the interfa- cial electron scattering for a number of metallic multi- layer structures were made in [1]. However, the data on this parameter obtained from electrical measurements are very limited. The discovery of the magnetorefrac- tive effect (MRE, r MRE ) in metallic layered nanostruc- tures [2] gave the possibility to study the spin asymme- try of the electron scattering based on IR optical mea- surements. Using the IR magnetoreflection method, we obtained the experimental data on the asymmetry of scattering of conduction electrons at the Fe/Cr(100) interface in the Fe(t x , Å)/Cr(10 Å) super- lattices (t Fe = 7.2–15.3 Å, t Cr = 10–23 Å) [3, 4]. In this work, we studied the Fe(t x , Å)/Cr(10 Å) superlattices with ultrathin Fe layers (t Fe < 7 Å). The earlier studies [5, 6] showed that the superlattices with ultrathin Fe layers exhibit unique magnetic and magnetotransport properties. At room temperature, these nanostructures are ideal superparamagnets, and, at low (liquid- helium) temperatures, they demonstrate properties of a cluster spin glass. The aim of this work is to study the magnetoresistive, optical, and magneto-optical prop- erties of the Fe(t x , Å)/Cr(10 Å) superlattices (t Fe =3.2, 2.6, and 2.1 Å) and to determine the parameters of the interfacial spin-dependent scattering of conduction electrons. 2. SAMPLE PREPARATION AND EXPERIMENTAL TECHNIQUE The studied MgO/Cr(80 Å)/[Fe(t x , Å)/Cr(10 Å)] n (n = 30–60) superlattices were prepared by molecular- beam epitaxy on a Katun-S high-vacuum setup. The substrates were single-crystal MgO(100) plates 30 × 30 × 0.5 mm in size. To decrease the surface roughness of the substrates, first, a buffer chromium layer with a thickness of approximately 80 Å was deposited on their surface. The subsequent alternating deposition of Fe and Cr layers was performed at a rate of approximately one atomic monolayer (ML) per minute. In all the nanostructures, the chromium layer thickness was constant and equal to 10 Å, which provided the forma- tion of antiparallel ordering of magnetic moments of neighboring Fe layers in the Fe/Cr superlattices (at H = 0) and, therefore, the highest magnitude of the magnetoresistive effect. The iron layer thicknesses were 3.2, 2.6, and 2.1 Å. Here and in what follows, we indicate in the text and the figures the nominal layer thicknesses determined from the deposition rate and time. The X-ray diffraction studies show that all the samples have a pronounced periodic structure. Figure 1 depicts the small-angle X-ray diffraction spectrum at the CoK α line typical for the nanostructures under study. The spectrum has a clear peak due to a period- icity of the multilayer structure. Figure 2a shows the magnetization curves of the superlattices studied in MAGNETISM Scattering of Conduction Electrons in Fe(t x , Å)/Cr(10 Å) Superlattices with Ultrathin Iron Layers I. D. Lobov*, M. M. Kirillova, A. A. Makhnev, L. N. Romashev, M. A. Milyaev, and V. V. Ustinov Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, ul. Sofii Kovalevskoi 18, Yekaterinburg, 620990 Russia e-mail: i_lobov@imp.uran.ru Received August 19, 2013 Abstract—IR magnetoreflection spectra, diagonal σ xx and off-diagonal σ xy components of the effective opti- cal conductivity tensor, and magnetic properties of Fe(t x , Å)/Cr(10 Å) superlattices have been studied. The abrupt decrease in the amplitude of dissipative function –ω Im σ xy (ω) (ω is the cyclic frequency of light wave) in the superlattices with ultrathin Fe layers (t Fe = 3.2, 2.6, 2.1 Å) has been analyzed. It has been found that the magnetorefractive effect in nanostructures with ultrathin iron layers is due to scattering of conduction electrons by magnetic interfacial layers formed in the Cr matrix with complete consumption of deposited iron atoms. The parameters of the interfacial scattering of electrons in the spin-up (↑) and spin-down (↓) conduc- tion channels have been discussed. DOI: 10.1134/S1063783414030172