Studying the structure and electrical conductivity of thin granulated bimetallic films

Gerke, M. N.; Istratov, A. V.; Bukharov, D. N.; Novikova, O. A.; Skryabin, I.; Аракелян, С. М.

doi:10.3103/s1062873817120127

Cited by 2 publications

(1 citation statement)

References 11 publications

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“…This is also the case for the films with compositions beyond the percolation threshold at temperatures of below ≈ 100 K. This fact may indicate an activation mechanism of electrical conductivity in the test films. However the experimentally observed curves cannot be approximated by a linear function in Mott's (Т -0.25 ) or Shelovskoi-Efros' (Т -0.5 ) coordinates and hence there is a more complex electrical conductivity mechanism in films with PZT matrix as compared with granular films of close compositions [11,12,[20][21][22][23][24]. The thermal dependences of the electrical resistivity of the oxidized FeCoZr-PZT films with x > x C exhibit an abrupt transition to a positive thermal coefficient of electrical resistivity at above 100 K which testifies to the presence of a contribution from metallic conductivity.…”

Section: Thermal and Field Dependences Of Electrical Resistivity Of Oxidized Fecozr-pzt Filmsmentioning

confidence: 99%

Effect of synthesis conditions and composition on structural and phase states and electrical properties of nanogranular (FeCoZr)x (PZT)100-x films (30 ≤ x ≤ 85 at.%)

Fedotova¹

2021

MoEM

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Granular films containing Fe50Co50Zr10 alloy nanoparticles inside Pb0,81Sr0,04(Na0,5Bi0,5)0,15(Zr0,575Ti0,425)O3 (PZT) ferroelectric matrix possess a combination of functional magnetic and electrical properties which can be efficiently controlled by means of external electric or magnetic fields. The formation of the required granular structure in PZT matrix is only possible if synthesis is carried out in an oxygen-containing atmosphere leading to substantial oxidation of metallic nanoparticles. Thus an important task is to study the oxidation degree of metallic nanoparticles depending on synthesis conditions and the effect of forming phases on the electrical properties of the films. The relationship between the structural and phase state and electrical properties of granular FeCoZr)x (PZT)100-x films (30 ≤ x ≤ 85 at.%) synthesized in an oxygen-containing atmosphere at the oxygen pressure PO in a range of (2.4–5.0) · 10–3 Pa has been studied using X-ray diffraction, EXAFS and four-probe electrical resistivity measurement. Integrated comparative analysis of the structural and phase composition and local atomic order in (FeCoZr)x (PZT)100-x films has for the first time shown the fundamental role of oxygen pressure PO during synthesis on nanoparticle oxidation and phase composition. We show that the oxygen pressure being within PO = 3.2 · 10–3 Pa an increase in x leads to a transition from nanoparticles of Fe(Co,Zr)O complex oxides to a superposition of complex oxides and a-FeCo(Zr,O) ferromagnetic nanoparticles (or their agglomerations). At higher oxygen pressures РО = 5.0 · 10–3 Pa the nanoparticles undergo complete oxidation with the formation of the (FexCo1-x)1-δO complex oxide having a Wurtzite structure. The forming structural and phase composition allows one to explain the observed temperature dependences of the electrical resistivity of granular films. These dependences are distinguished by a negative temperature coefficient of electrical resistivity over the whole range of film compositions at a high oxygen pressure (РО = 5.0 · 10–3 Pa) and a transition to a positive temperature coefficient of electrical resistivity at a lower oxygen pressure (РО = 3.2 · 10–3 Pa) in the synthesis atmosphere and x > 69 at.% in the films. The transition from a negative to a positive temperature coefficient of electrical resistivity which suggests the presence of a metallic contribution to the conductivity is in full agreement with the X-ray diffraction and EXAFS data indicating the persistence of unoxidized a-FeCo(Zr,O) ferromagnetic nanoparticles or their agglomerations.

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Section: Thermal and Field Dependences Of Electrical Resistivity Of Oxidized Fecozr-pzt Filmsmentioning

confidence: 99%

Effect of synthesis conditions and composition on structural and phase states and electrical properties of nanogranular (FeCoZr)x (PZT)100-x films (30 ≤ x ≤ 85 at.%)

Fedotova¹

2021

MoEM

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Influence of preparation regimes and composition on structure, phase state and electric properties of nanogranular (FeCoZr)x(PZT)100-x (30 ≤ x ≤ 85 at.%) films

Fedotova

2021

Izv. vysš. učebn. zaved., Mater. èlektron. teh.

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Granular films containing Fe50Co50Zr10 alloy nanoparticles inside the ferroelectric matrix Pb0.81Sr0.04(Na0.5Bi0.5)0.15(Zr0.575Ti0.425)O3 (PZT) are characterized by a complex of functional magnetic and electrical characteristics that can be effectively controlled by an external electric or magnetic field. The formation of the necessary granular structure in the case of a PZT matrix is possible only during synthesis in an oxygen-containing atmosphere, leading to significant oxidation of metal nanoparticles. In this regard, an urgent task is to study the degree of oxidation of metal nanoparticles depending on the synthesis conditions, as well as the influence of the forming phases on the electrical properties of films.The relationship of the phase composition and electrical characteristics of granular films (FeCoZr)x(PZT)100-x (30 ≤ x ≤ 85, at.%) obtained in an oxygen-containing atmosphere at a pressure of PO in the range (2.4—5.0) ⋅ 10-3 Pa was studied by X-ray diffraction analysis, EXAFS spectroscopy (Extended X-ray Absorption Fine Structure) and four-probe electrical resistivity measurements.A comparative complex analysis of the structural-phase composition and local atomic order in films (FeCoZr)x(PZT)100-x for the first time showed the fundamental influence of oxygen pressure during synthesis on the oxidation of nanoparticles and their phase composition. It is shown that in the case of oxygen pressure up to the values of PO = 3.2 ⋅ 10-3 Pa, a transition from nanoparticles of complex Fe(Co,Zr) oxides occurs with increasing x to the superposition of complex oxides and ferromagnetic nanoparticles α-FeCo(Zr,O) (or their agglomerations). At a higher oxygen pressure PO = 5.0 ⋅ 10-3 Pa, complete oxidation of nanoparticles is observed with the formation of a complex oxide (FexCo1-x)1-δO with a wustite structure.The observed structural-phase composition allows us to explain the measured temperature dependences of the electrical resistance of granular films, characterized by a negative temperature coefficient of electrical resistance (TKR) in the entire range of film compositions at high oxygen pressure (PO = 5.0 ⋅ 10-3 Pa), and the transition to positive TKR at lower oxygen pressure (PO = 3.2 ⋅ 10-3 Pa) in the synthesis atmosphere and the value x ≤ 69 at.% in films. The transition from negative to positive TKR, indicating the presence of a metallic contribution to conductivity, is fully correlated with the detection by XRD and EXAFS methods of non-oxidized ferromagnetic nanoparticles α-FeCo(Zr,O) or their agglomerations.

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Studying the structure and electrical conductivity of thin granulated bimetallic films

Cited by 2 publications

References 11 publications

Effect of synthesis conditions and composition on structural and phase states and electrical properties of nanogranular (FeCoZr)x (PZT)100-x films (30 ≤ x ≤ 85 at.%)

Effect of synthesis conditions and composition on structural and phase states and electrical properties of nanogranular (FeCoZr)x (PZT)100-x films (30 ≤ x ≤ 85 at.%)

Influence of preparation regimes and composition on structure, phase state and electric properties of nanogranular (FeCoZr)x(PZT)100-x (30 ≤ x ≤ 85 at.%) films

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