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.%)
Open Access
- 30 September 2021
- journal article
- Published by Pensoft Publishers in Modern Electronic Materials
- Vol. 7 (3), 91-97
- https://doi.org/10.3897/j.moem.7.3.76277
Abstract
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.This publication has 22 references indexed in Scilit:
- Magnetic properties and anisotropic coercivity in nanogranular films of Co/Al2O3above the percolation limitJournal of Physics D: Applied Physics, 2014
- Negative capacitance in (FeCoZr)–(PZT) nanocomposite filmsJournal of Physics D: Applied Physics, 2013
- Electron transport properties of magnetic granular filmsScience China Physics Mechanics and Astronomy, 2012
- Effect of oxygen pressure on phase composition and magnetic structure of FeCoZr-Pb(ZrTi)O3 nanocompositesPhysics of the Solid State, 2012
- Magnetoresistance in FeCoZr–Al2O3 nanocomposite films containing ‘metal core–oxide shell’ nanogranulesJournal of Physics D: Applied Physics, 2011
- Effect of oxide shells on the magnetic and magnetotransport characteristics of oxidized FeCoZr nanogranules in Al2O3Journal of Alloys and Compounds, 2011
- Magnetoresistance and electronic structure of granular films with MgO or MgF2matricesJournal of Physics: Conference Series, 2011
- Phase transitions in xPbZr0.53Ti0.47O3-(1 − x)Mn0.4Zn0.6Fe2O4 magnetoelectric compositesPhysics of the Solid State, 2009
- Tuning of magnetic properties and structure of granular FeCoZr–Al2O3 nanocomposites by oxygen incorporationJournal of Alloys and Compounds, 2009
- CoFe2O4 nanoparticles prepared by the mechanochemical methodJournal of Alloys and Compounds, 2000