The Features of Real Part of Admittance in the Nanocomposites (Fe₄₅Co₄₅Zr₁₀)_x(Al₂O₃)_{100 - x}Manufactured by the Ion-Beam Sputtering Technique with Ar Ions

Abstract

The temperature and frequency dependences of the admittance real part σ(T, f ) in granular (Fe 45 Co 45 Zr 10 ) x (Al 2 O 3 ) 100−x nanocomposite films around the percolation threshold x C were investigated. The behaviour of σ(T, f ) vs. the temperature and frequency over the ranges 77-300 K and 50 Hz-1 MHz, respectively, displays the predominance of an activation (hopping) conductance mechanism for the samples below the percolation threshold x C and of a metallic one beyond the x C determined as 54 ± 2 at.%. The mean hopping range d for the nanoparticles diameter D was estimated at different metallic phase content x.

AC Hopping Conductance in Nanocomposite Films with Ferromagnetic Alloy Nanoparticles in a PbZrTiO3 Matrix

“…The method to manufacture the films and the characterization of their structures are described in detail elsewhere. 15,[26][27][28] The compound target contained Fe 45 Co 45 Zr 10 alloy plates with PbZrTiO 3 stripes arranged on their surfaces. The irregular distribution of the PbZrTiO 3 stripes (with continuously increasing spaces between them) on the target surfaces allows synthesis of films with variable metalto-dielectric ratios, x (depending on the mutual arrangement of the targets and substrates) in one technological cycle.…”

“…In our earlier studies on (Fe 45 Co 45 Zr 10 ) x (Al 2 O 3 ) (100Àx) nanocomposite granular films, 8,[13][14][15][16] it was shown that deposition conditions play the key role in the phase composition of the films. In particular, transmission electron microscopy, x-ray diffraction (XRD) analysis, and Mössbauer spectroscopy (MS) measurements revealed that adding oxygen to the sputtering atmosphere results in formation of CoFe-based oxide shells around the FeCoZr nanoparticles.…”

“…[18][19][20] The observation of NC is associated with a dominant inductive-like (L) contribution in the imaginary part of the admittance, which could be utilized to produce microscale planar inductive elements in electrical engineering of integrated circuits. It has been proved that the dominant L-contribution is related to the formation of the core/shell structure of the nanoparticles; 8,[13][14][15][16]19,20 namely, it strongly increased with growth of the semiconducting CoFe-based oxide shell thickness. Technologically, the formation of the core/ shell nanoparticle structure can be obtained by either annealing in air (for FeCoZr-alumina and FeCoZrCaF 2 nanocomposites 15,21 ) or adding oxygen to the atmosphere during synthesis (for FeCoZr-PbZrTiO 3 nanocomposites 17,19,22 ).…”

“…It has been proved that the dominant L-contribution is related to the formation of the core/shell structure of the nanoparticles; 8,[13][14][15][16]19,20 namely, it strongly increased with growth of the semiconducting CoFe-based oxide shell thickness. Technologically, the formation of the core/ shell nanoparticle structure can be obtained by either annealing in air (for FeCoZr-alumina and FeCoZrCaF 2 nanocomposites 15,21 ) or adding oxygen to the atmosphere during synthesis (for FeCoZr-PbZrTiO 3 nanocomposites 17,19,22 ). The experimentally observed frequency dependences of admittance with NC in as-deposited and annealed FeCoZr-alumina and as-deposited FeCoZr-PbZrTiO 3 nanocomposite films can be explained by the hopping AC conductance model developed in Refs.…”

“…The presence of the NC effect in as-deposited and annealed (Fe 45 Co 45 Zr 10 ) x (Al 2 O 3 ) (100Àx) films can be primarily controlled by the volume ratio and the phase composition of the oxide shells around the metallic nanoparticles; [7][8][9][13][14][15][16][17]22 namely, the shells should have semiconducting properties and be as thick as possible. In addition, the phase composition and volume contribution of the shells depend on several factors: (1) the composition of the films with respect to the percolation threshold (progressive oxidation of metallic nanoparticles with x growth is shown in Ref.…”