arXiv subjects

Ihor V. Fesych

Publications and source records attributed to Ihor V. Fesych.

3 recordsLinked to original sources

arXiv2026

A colossal dielectric response of Bi1-xSmxFeO3 nanopowders

The dielectric permittivity of the pressed powder samples of Bi1-xSmxFeO3, with Sm content "x" varying in the range 0 - 0.2, has been investigated in the temperature range from 20 to 400 C and the frequency range from 100 Hz to 100 kHz. We have shown that the Sm content impacts significantly the real and imaginary parts of effective dielectric permittivity, which have expanded diffuse maxima with a colossal magnitude up to 105 (for the real part) and up to 108 (for the imaginary one) at temperatures 300 - 400 K. Analysis of experimental data carried has shown that both the real and imaginary parts of effective dielectric permittivity may be comprehensively explained by considering a complex interplay of a diffuse ferroelectric-paraelectric phase transition and the Maxwell-Wagner-Sillars effects, which emerge from the formation of spatial charges at interfaces between nanograins and at the ferroelectric nanoparticle-air interface. Processing of experimental data for the real and imaginary parts of the effective dielectric permittivity within effective medium approach allows us to separate and analyze the colossal dielectric response of the nanoparticles itself. The main trends followed from experiments are supported by the theoretically simulated dependences, which reveal correlations between the temperature behavior of dielectric properties and phase state of the Bi1-xSmxFeO3 nanoparticles.

cond-mat.mtrl-sci↗

arXiv2026

Correlations Between the Dielectric Properties, Domain Structure Morphology and Phase State of Bi1-xSmxFeO3 Nanoparticles

Nanoscale multiferroics are basic model objects for studying polar, magnetic and magnetoelectric properties and mutual couplings. Bismuth-samarium ferrite (Bi1-xSmxFeO3) is a model orthoferrite, whose polar, magnetic and magnetoelectric properties have been studied for the bulk and thin film samples. The properties of Bi1-xSmxFeO3 nanoparticles have been much less studied, despite the nanoparticles can be used in a wide range of applications, such as energy storage, magnetic hyperthermia and advanced nanoelectronics. In this work we performed experimental measurements and analysis of the temperature dependence of the Bi1-xSmxFeO3 nanopowders dielectric properties. Calculations of the ferro-ionic coupling influence on the dielectric properties, domain structure morphology and phase states are performed in the framework of the Ginzburg-Landau-Devonshire-Stephenson-Highland approach. Theoretical results explain the main trends of experimentally observed temperature dependences of the effective dielectric permittivity, which allows us to understand the correlations between the temperature behavior of dielectric properties, domain structure morphology and phase state of Bi1-xSmxFeO3 nanoparticles.

cond-mat.mtrl-sci↗

arXiv2025

Resistive switching and charge accumulation in Hf0.5Zr0.5O2 nanoparticles

We revealed the resistive switching, negative differential resistance and charge accumulation effects in Hf0.5Zr0.5O2 nanopowders sintered by the auto-combustion sol-gel method and annealed at temperatures from 500°C to 800°C. The fraction of the orthorhombic phase, determined by the X-ray diffraction (XRD), decreases from 91 vol.% to 7 vol.% with an increase in the annealing temperature from 600°C to 800°C. The electron paramagnetic resonance (EPR) spectra reveal the great amount of oxygen vacancies in the annealed samples, at that the decrease of the orthorhombic phase fraction (observed with an increase in the annealing temperature) correlates with a decrease in the intensity of EPR spectral lines associated with the oxygen vacancies and impurities. This indicates the participation of oxygen vacancies and other defects in the formation of the orthorhombic phase in the Hf0.5Zr0.5O2 powders. To explain the results of electrophysical measurements, we compare the features of the current-voltage characteristics with the phase composition of the Hf0.5Zr0.5O2 powders and with the peculiarities of their EPR spectra. The analysis allows us to relate the resistive switching and charge accumulation observed in Hf0.5Zr0.5O2 nanopowders with the appearance of the ferroelectric-like polar regions in the orthorhombic phase of the nanoparticles, which agrees with the calculations performed in the framework of Landau-Ginzburg-Devonshire approach and density functional theory.

cond-mat.mtrl-sci↗