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

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 x 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 ae 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 ae 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) ae 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 > 10(4) 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 10(5) at a resistance ratio R (off)/R (on) similar to 50.