Transport, Magnetic, and Memristive Properties of a Nanogranular [.sub.100 - x] Composite Material

The properties of [(CoFeB).sub.x][(LiNb[O.sub.y]).sub.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 nanocompo...

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Published in:Journal of experimental and theoretical physics 2018-03, Vol.126 (3), p.353
Main Authors: Rylkov, V.V, Nikolaev, S.N, Demin, V.A, Emelyanov, A.V, Sitnikov, A.V, Nikiruy, K.E, Levanov, V.A, Presnyakov, M.Yu, Taldenko, A.N, Vasiliev, A.L, Chernoglazov, K.Yu, Vedeneev, A.S, Kalinin, Yu.E, Granovsky, A.B, Tugushev, V.V, Bugaev, A.S
Format: Article
Language:English
Subjects:
ALLOYS
Analysis
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
CMS DETECTOR
COBALT IONS
COMPOSITE MATERIALS
ELECTRIC CONDUCTIVITY
ELECTRIC POTENTIAL
Electrical conductivity
Ferromagnetism
HALL EFFECT
IRON IONS
MAGNETIZATION
MATERIALS SCIENCE
Movies
NANOCOMPOSITES
TEMPERATURE DEPENDENCE
TUNNEL EFFECT
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Summary:The properties of [(CoFeB).sub.x][(LiNb[O.sub.y]).sub.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 LiNb[O.sub.y] matrix with a high content of [Fe.sup.2+] and [Co.sup.2+] magnetic ions (up to 3 x [10.sup.22] [cm.sup.-3]). At T [less than or equal to] 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 [approximately equal to] 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 [approximately equal to] 10- 200 K on the metallic side of the metal-insulator transition (44 at % < x < 48 at %) is described by a logarithmic law [sigma](T) [varies] lnT. This law changes into the law of "1/2" at x [less than or equal to] 40 at %. The tunneling anomalous Hall effect is strongly suppressed and the longitudinal conductivity turns out to be lower than in a [(CoFeB).sub.x][(Al[O.sub.y]).sub.100 - x] composite material by an order of magnitude. The capacitor structures based on [(CoFeB).sub.x][(LiNb[O.sub.y]).sub.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 > [10.sup.4] V/cm because of the suppression of Coulomb blockage effects and the generation of oxygen vacancies [V.sub.O] and (ii) the injection (or extraction) of [V.sub.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.sub.off]/[R.sub.on] ~ 50. DOI: 10.1134/S1063776118020152
ISSN:1063-7761
1090-6509
DOI:10.1134/S1063776118020152