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Scaling of anomalous Hall effect as a method to determine percolation threshold and metal—insulator transition in magnetic nanocomposites with intergranular interactiona National Research Centre ‘Kurchatov Institute’, pl. akad. Kurchatova 1, Moscow, 123182, Russian Federation b P.L. Kapitza Institute for Physical Problems, Russian Academy of Sciences, ul. Kosygina 2, Moscow, 119334, Russian Federation c HSE University, ul. Myasnitskaya 20, Moscow, 101000, Russian Federation d Voronezh State Technical University, Moskovskii prosp. 14, Voronezh, 394026, Russian Federation e Moscow Institute of Physics and Technology (National Research University), Institutskii per. 9, Dolgoprudny, Moscow Region, 141701, Russian Federation f Lomonosov Moscow State University, Faculty of Physics, Leninskie Gory 1 build. 2, Moscow, 119991, Russian Federation g Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, ul. Izhorskaya 13/19, Moscow, 127412, Russian Federation h Kotelnikov Institute of Radioengineering and Electronics of the Russian Academy of Sciences, ul. Mokhovaya 11, kor. 7, Moscow, 125009, Russian Federation Using the example of nanocomposite (NC) films (CoFeB)x(LiNbO3)100−x, in which at relatively high temperatures of T ≿ 10 K a 'weakly insulating' regime is observed in the logarithmic temperature dependence of the conductivity σ ∝ ln T, characteristic of a strong tunnel coupling between granules, the scaling in the behavior of the anomalous Hall effect (AHE) resistance as a function of the longitudinal resistance ρAHE was studied in detail. The studies were carried out in fields up to 14 T at temperatures T = 0.4—200 K in the range of metallic phase content x ≈ 35—60 at.%, covering the percolation transition. It was found that the power n in the scaling dependence ρAHE ∝[ρ(T)]n behaves nonmonotonically. In the ranges x ≈ 35—44 at.% and x ≈ 50—60 at.%, an increase in the power is clearly observed, whereas in the interval x ≈ 44—50 at.%, the value of n remains practically unchanged. We believe that the kink regions in the dependence n(x) indicate a change in the NC conductivity mechanism and determine the percolation threshold (at xp ≈ 50 at.%) and the metal—insulator transition (xc ≈ 43—44 at.%), which do not coincide in these systems. The results of an analysis of the behavior of σ (T) at subhelium temperatures T = 0.4—3 K confirm this conclusion. Studies of the magnetic properties of NCs vs the metallic phase content x using ferromagnetic resonance and magneto-optical spectroscopy methods also indicate the pres„ence of specific features in the vicinity of concentrations x ≈ 44 and 50 at.%.
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