arXiv subjects

Yuri O. Zagorodniy

Publications and source records attributed to Yuri O. Zagorodniy.

4 recordsLinked to original sources

arXiv2026

Magnetic properties and charge transport mechanisms in oxygen-deficient HfxZr1-xO2-y nanoparticles

Study of nanoscale hafnia-zirconia physical properties is the key topic in fundamental and applied science. However, charge transport mechanisms and magnetic properties of hafnia-zirconia nanoparticles are very poorly studied both theoretically and experimentally. In this work we observed a superparamagnetic-like and superparaelectric-like response of ultra-small hafnia-zirconia nanoparticles prepared by the solid-state organonitrate synthesis. The EPR spectra of hafnia-zirconia nanopowders reveal the presence of paramagnetic defect centers, which may be hafnium and/or zirconium ions, which trapped an electron near an oxygen vacancy and changed their valence state from the non-paramagnetic +4 to the paramagnetic +3 state. The Raman spectra indicate the decisive role of surface defects, presumably oxygen vacancies, for all studied Zr compositions.At the same time the EELS analysis does not reveal any noticeable concentration of magnetic impurities in the hafnia-zirconia nanopowders, and the X-ray diffraction analysis reveals the dominant presence of the orthorhombic phase. We observed that the quasi-static relative dielectric permittivity of the hafnia-zirconia nanopowders overcomes 10^6 - 10^7 and related the colossal values with the superparaelectric state of the nanoparticles cores induced by the flexo-electro-chemical strains. It has been found that ultra-small hafnia-zirconia nanoparticles reveal posistor effect and relatively large values of accumulated charge. Thus, obtained results open the way for creation of silicon-compatible ferroics oxygen-deficient hafnia-zirconia nanoparticles with superparamagnetic and superparaelectric properties, which may be used in advanced FETs and electronic logic elements.

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↗

arXiv2024

The origin of the ferroelectric-like orthorhombic phase in oxygen-deficient HfO2-y nanoparticles

In this work we established the relationship between the crystalline structure symmetry, point defects and possible appearance of the ferroelectric-like polarization in HfO2-y nanoparticles. Notably, that XRD and EPR analysis revealed the formation of the ferroelectric-like orthorhombic phase in the oxygen-deficient HfO2-y nanoparticles (pure and doped with rare-earth element yttrium). DFT calculations showed that small HfO2 nanoparticles may become polar, especially in the presence of impurity atoms and/or oxygen vacancies. To explain the experimental results, we have modified the effective LGD model through the parameterization approach, focusing on the Landau expansion coefficients associated with the polar (FE) and antipolar (AFE) orderings, which agrees with the performed DFT calculations. The effective LGD model can be useful for the development of the novel generation of silicon-compatible ferroelectric nanomaterials based on the HfxZr1-xO2-y.

cond-mat.mtrl-sci↗

arXiv2024

Phase diagrams and polarization reversal in nanosized Hf$_x$Zr$_{1-x}$O$_{2-y}$

To describe the polar properties of the nanosized HfxZr1-xO2-y, we evolve the "effective" Landau-Ginzburg-Devonshire (LGD) model based on the parametrization of the Landau expansion coefficients for the polar and antipolar orderings. We have shown that the effective LGD model can predict the influence of screening conditions and size effects on phase diagrams, polarization reversal and structural properties of the nanosized HfxZr1-xO2-y of various shape and sizes. To verify the model, we use available experimental results for HfxZr1-xO2 thin films and oxygen-deficient HfO2-y nanoparticles prepared at different annealing conditions. X-ray diffraction, which was used to determine the phase composition of the HfO2-y nanoparticles, revealed the formation of the ferroelectric orthorhombic phase in them. Micro-Raman spectroscopy was used to explore the correlation of lattice dynamics and structural changes appearing in dependence on the oxygen vacancies concentration in the HfO2-y nanoparticles. Since our approach allows to determine the conditions (shape, sizes, Zr content and/or oxygen vacancies amount) for which the nanosized HfxZr1-xO2-y are ferroelectrics or antiferroelectrics, we hope that obtained results are useful for creation of next generation of Si-compatible ferroelectric gate oxide nanomaterials.

cond-mat.mes-hall↗