Scaling of anomalous Hall effect as a method to determine percolation threshold and metal—insulator transition in magnetic nanocomposites with intergranular interaction

S.N. Nikolaev^†^a, A.B. Drovosekov^b, M.Yu. Dmitrieva^b, c, K.Yu. Chernoglazov^a, A.V. Sitnikov^a, d, A.N. Taldenkov^a, A.L. Vasiliev^a, e, E.A. Gan’shina^f, I.M. Pripechenkov^f, M.A. Simdyanova^f, A.B. Granovsky^f, g, V.V. Rylkov^‡^a, g, h
^aNational Research Centre ‘Kurchatov Institute’, pl. akad. Kurchatova 1, Moscow, 123182, Russian Federation
^bP.L. Kapitza Institute for Physical Problems, Russian Academy of Sciences, ul. Kosygina 2, Moscow, 119334, Russian Federation
^cHSE University, ul. Myasnitskaya 20, Moscow, 101000, Russian Federation
^dVoronezh State Technical University, Moskovskii prosp. 14, Voronezh, 394026, Russian Federation
^eMoscow Institute of Physics and Technology (National Research University), Institutskii per. 9, Dolgoprudny, Moscow Region, 141701, Russian Federation
^fLomonosov Moscow State University, Faculty of Physics, Leninskie Gory 1 build. 2, Moscow, 119991, Russian Federation
^gInstitute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, ul. Izhorskaya 13/19, Moscow, 127412, Russian Federation
^hKotelnikov 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 ρ_AHE 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 ρ_AHE ∝[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 x_p ≈ 50 at.%) and the metal—insulator transition (x_c ≈ 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.%.

Keywords: anomalous Hall effect, nanocomposites, metal—insulator transition, percolation threshold
PACS: 64.60.ah, 71.30.+h, 75.47.−m (all)
DOI: 10.3367/UFNe.2024.11.039814
URL: https://ufn.ru/en/articles/2025/6/f/
Web of Science

001570951300008
Scopus

2-s2.0-105011964867
ADS NASA

2025PhyU...68..617N
Citation: Nikolaev S N, Drovosekov A B, Dmitrieva M Yu, Chernoglazov K Yu, Sitnikov A V, Taldenkov A N, Vasiliev A L, Gan’shina E A, Pripechenkov I M, Simdyanova M A, Granovsky A B, Rylkov V V "Scaling of anomalous Hall effect as a method to determine percolation threshold and metal—insulator transition in magnetic nanocomposites with intergranular interaction" Phys. Usp. 68 617–626 (2025)

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Received: 14th, August 2024, accepted: 23rd, November 2024

Оригинал: Николаев С Н, Дровосеков А Б, Дмитриева М Ю, Черноглазов К Ю, Ситников А В, Талденков А Н, Васильев А Л, Ганьшина Е А, Припеченков И М, Симдянова М А, Грановский А Б, Рыльков В В «Cкейлинг аномального эффекта Холла как метод определения порога перколяции и перехода металл—изолятор в магнитных нанокомпозитах с межгранульным взаимодействием» УФН 195 658–668 (2025); DOI: 10.3367/UFNr.2024.11.039814