Transport, Magnetic, and Memristive Properties of a Nanogranular (CoFeB)  x  (LiNbO  y  ) 100– x   Composite Material

V. V. Rylkov; S. N. Nikolaev; V. A. Demin; A. V. Emelyanov; A. V. Sitnikov; K. E. Nikiruy; V. A. Levanov; M. Yu. Presnyakov; A. N. Taldenkov; A. L. Vasiliev; K. Yu. Chernoglazov; A. S. Vedeneev; Yu. E. Kalinin; A. B. Granovsky; V. V. Tugushev; A. S. Bugaev

doi:10.1134/S1063776118020152

Transport, Magnetic, and Memristive Properties of a Nanogranular (CoFeB)_x(LiNbO_y)_100–x Composite Material

Authors: Rylkov V.V.¹^,2, Nikolaev S.N.¹, Demin V.A.¹, Emelyanov A.V.¹, Sitnikov A.V.³, Nikiruy K.E.¹^,4, Levanov V.A.¹^,5, Presnyakov M.Y.¹, Taldenkov A.N.¹, Vasiliev A.L.¹, Chernoglazov K.Y.¹, Vedeneev A.S.², Kalinin Y.E.³, Granovsky A.B.⁵, Tugushev V.V.¹, Bugaev A.S.⁴^,2
Affiliations:
1. National Research Centre “Kurchatov Institute,”
2. Fryazino Branch, Kotelnikov Institute of Radio Engineering and Electronics
3. Voronezh State Technical University
4. Moscow Institute of Physics and Technology
5. Moscow State University
Issue: Vol 126, No 3 (2018)
Pages: 353-367
Section: Order, Disorder, and Phase Transition in Condensed System
URL: https://journals.rcsi.science/1063-7761/article/view/192911
DOI: https://doi.org/10.1134/S1063776118020152
ID: 192911

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Abstract

The properties of (CoFeB)_x(LiNbO_y)_100–x nanocomposite films with a ferromagnetic alloy content x = 6–48 at % are comprehensively studied. The films are shown to consist of ensembles of CoFe granules 2–4 nm in size, which are strongly elongated (up to 10–15 nm) in the nanocomposite growth direction and are located in an LiNbO_y matrix with a high content of Fe²⁺ and Co²⁺ magnetic ions (up to 3 × 1022 cm^–3). At T ≤ 25 K, a paramagnetic component of the magnetization of nanocomposites is detected along with a ferromagnetic component, and the contribution of the former component is threefold that of the latter. A hysteresis of the magnetization is observed below the percolation threshold up to x ≈ 33 at %, which indicates the appearance of a superferromagnetic order in the nanocomposites. The temperature dependence of the electrical conductivity of the nanocomposites in the range T ≈ 10–200 K on the metallic side of the metal–insulator transition (44 at % < x < 48 at %) is described by a logarithmic law σ(T) ∝ lnT. This law changes into the law of “1/2” at x ≤ 40 at %. The tunneling anomalous Hall effect is strongly suppressed and the longitudinal conductivity turns out to be lower than in a (CoFeB)_x(AlO_y)_100–x composite material by an order of magnitude. The capacitor structures based on (CoFeB)_x(LiNbO_y)_100–x films exhibit resistive switching effects. They are related to (i) the formation of isolated chains of elongated granules and an anomalously strong decrease in the resistance in fields E > 10⁴ V/cm because of the suppression of Coulomb blockage effects and the generation of oxygen vacancies V_O and (ii) the injection (or extraction) of V_O vacancies (depending on the sign of voltage) into a strongly oxidized layer in the nanocomposites, which is located near an electrode of the structure and controls its resistance. The number of stable resistive switchings exceeds 10⁵ at a resistance ratio R_off/R_on ~ 50.

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Transport, Magnetic, and Memristive Properties of a Nanogranular (CoFeB)x(LiNbOy)100–x Composite Material

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Abstract

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Transport, Magnetic, and Memristive Properties of a Nanogranular (CoFeB)_x(LiNbO_y)_100–x Composite Material