arXiv subjects

Priyanka Yadav

Publications and source records attributed to Priyanka Yadav.

6 recordsLinked to original sources

arXiv2026

Unraveling the temperature-responsive charge-disproportionation in BaBiO$_3$

This study shows that the charge disproportionation at the Bi site in BaBiO$_3$ alters as a function of temperature. Decreasing the temperature from 300K down to 160K leads to a significant modification of the density of states corresponding to the Bi-O hybridized band near the Fermi level (E$_\text{F}$). This modification indicates reduction of Bi 6$sp$ - O 2$p$ hybridization and O 2$p$ spectral weight near E$_\text{F}$. The strong decrement of covalency at lower temperatures is accompanied by a decrement in O 2$p$ hole density due to possible charge transfer from Bi 6$s$ to the O 2$p$ band. Bi-charge state analysis from Bi-4$f$ core-level spectra showed that at 300K, $δ$ (charge difference between alternate Bi sites) value in 4$\pmδ$ is much less than at 160K, which reveals the transition towards the ionic nature of CD or static CD in BBO at low temperature. On the other hand, O 1$s$ core-level spectra displayed an asymmetric shape, and temperature-dependent modifications of the asymmetric shape and intensity have been observed. This highlights the significant influence of the O 2$p$ band hole on the dynamical CD at the Bi site.

cond-mat.mtrl-sci↗

arXiv2026

Magnetic, transport and electronic properties of Ni$_2$FeAl Heusler alloy nanoparticles: Experimental and theoretical investigation

We present a comprehensive investigation of structural, magnetic and transport properties of Ni$_2$FeAl Heusler alloy nanoparticles (NPs) synthesized via template-less chemical route. The NPs exhibit high saturation magnetization of 3.02 $μ_ {\rm B}$/f.u. at 5~K, large magnetic anisotropy of 0.238 MJ/m$^3$, and a Curie temperature of 874~K. Magnetocaloric analysis reveals a magnetic entropy change of 3.1 J.kg$^{-1}$K$^{-1}$ at 70 kOe. Low-temperature transport measurements show a weak resistivity upturn, following a $-T^{1/2}$ dependence, indicative of disorder-enhanced electron-electron interactions. First-principles calculations based on density functional theory yield a magneto-crystalline anisotropy energy of 0.987 MJ/m$^3$, consistent with experiment and demonstrate pronounced surface and finite-size effects through comparison of bulk and nanocluster geometries. The combination of high Curie temperature, sizable perpendicular magnetic anisotropy, and moderate spin polarization and magnetic entropy change make the Ni$_2$FeAl as promising candidate for various applications.

cond-mat.mtrl-sci↗

arXiv2026

Role of Disorder in Governing the Magnetic Properties of Cu2IrO3

Cu$_2$IrO$_3$ is a honeycomb iridate which has been studied recently as a candidate Kitaev quantum spin liquid. Its magnetic ground state however, has been reported to be quantum disordered, spin glassy, or magnetically ordered depending on synthesis details. We have prepared a Cu$_2$IrO$_3$ sample with large antisite disorder and studied in detail its structure (global and local), charge states, and thermodynamic properties to try to quantify and characterize the disorder and its connection to the magnetic ground state. X-ray diffraction, Extended x-ray absorption fine structure(EXAFS) and X-ray pair distribution function analysis revealed a large site disorder ($\sim$25\%), while XPS and XANES reveal mixed valence of Cu and Ir following Cu$^{1+}$ + Ir$^{4+}$ $\rightarrow$ Cu$^{2+}$ + Ir$^{3+}$. This combination of site disorder and charge redistribution generates competing antiferromagnetic interactions and magnetic frustration, resulting in dynamically fluctuating AFM clusters near 80K that freeze below 29K. These results demonstrate the crucial role of synthesis dependent disorder in determining the magnetic ground state of Cu$_2$IrO$_3$.

cond-mat.str-el↗

arXiv2024

Magnetic correlations and Griffith-like phase in Co$_2$TiSi$_{0.5}$Al$_{0.5}$ Heusler alloy

We present a comprehensive study aimed at elucidating the complex magnetic correlations in Co$_2$TiSi$_{0.5}$Al$_{0.5}$ Heusler alloy having the partial B2-type structure amid L2$_1$ cubic main phase. The thermo-magnetization measurements at 100 Oe reveal the presence of two magnetic transitions at T$\rm_{C1}=278~K$ and T$\rm_{C2}=270~K$, respectively, with saturation magnetization of around 1.2 $μ\rm_ B$/f.u. at 5~K. Our magnetic field dependent studies reveal the dominance of T$\rm_{C1}$ transition at lower fields ($μ_0\rm H \leqslant 0.03~Tesla$); however, at higher fields the T$\rm_{C2}$ transition becomes more pronounced. The observation of remnant magnetization above Curie temperature suggests the development of Griffiths-like phase, which is extensively analyzed through {\it ac} and {\it dc}- magnetic susceptibility ($χ$) data. The evaluation of magnetocaloric potential indicates second order phase transition with notable $ΔS_{\rm M}=$ 2.22 Jkg$^{-1}$K$^{-1}$ at 7 Tesla. The low-field ($μ_0\rm H \leqslant 0.1~Tesla$) magnetic entropy ($ΔS_{\rm M}$) curves exhibit two non-identical positive peaks. The nature and range of spin interactions near T$\rm_C$ were scrutinized through rigorous critical phenomenon analysis, and the values of exponents $α, β, γ$ and $δ$ to be $0.063, 0.361, 1.108$ and $3.943$, respectively, which are found to be slightly deviating from mean-field theory towards 3D Heisenberg model. Additionally, the exchange magnetic interactions are found to decay as $J(r) \sim r^{-4.6}$. Furthermore, the density functional theory results reveal the half-metallic nature exhibiting 100\% spin polarization (SP). However, the electronic and magnetic properties are greatly affected by the incorporation of structural disorder, which results in drastic reduction of SP to mere 8.3\%.

cond-mat.str-el↗

arXiv2022

A Hybrid CNN-LSTM model for Video Deepfake Detection by Leveraging Optical Flow Features

Deepfakes are the synthesized digital media in order to create ultra-realistic fake videos to trick the spectator. Deep generative algorithms, such as, Generative Adversarial Networks(GAN) are widely used to accomplish such tasks. This approach synthesizes pseudo-realistic contents that are very difficult to distinguish by traditional detection methods. In most cases, Convolutional Neural Network(CNN) based discriminators are being used for detecting such synthesized media. However, it emphasise primarily on the spatial attributes of individual video frames, thereby fail to learn the temporal information from their inter-frame relations. In this paper, we leveraged an optical flow based feature extraction approach to extract the temporal features, which are then fed to a hybrid model for classification. This hybrid model is based on the combination of CNN and recurrent neural network (RNN) architectures. The hybrid model provides effective performance on open source data-sets such as, DFDC, FF++ and Celeb-DF. This proposed method shows an accuracy of 66.26%, 91.21% and 79.49% in DFDC, FF++, and Celeb-DF respectively with a very reduced No of sample size of approx 100 samples(frames). This promises early detection of fake contents compared to existing modalities.

cs.CV↗

arXiv2022

Role of local structural distortions on the origin of j=1/2 pseudo-spin state in sodium iridate

Na2IrO3 (NIO) is known to be a spin-orbit (SO) driven j=1/2 pseudo-spin Mott-Hubbard (M-H) insulator. However, the microscopic origin of the pseudo-spin state and the role of local structural distortions have not been clearly understood. Using a combination of theoretical calculations and x-ray spectroscopy, we show that the energetics in the vicinity of Fermi level (EF) is governed by SO interactions, electron correlation and local octahedral distortions. Contrary to the earlier understanding, here we show that the j=3/2 and 1/2 pseudo-spin states have admixture of both t2g and eg characters due to local structural distortion. Reduction of local octahedral symmetry also enables Ir 5d- O2p hybridization around the EF resulting in a M-H insulator with enhanced charge transfer character. The possibility of Slater insulator phase is also ruled out by a combination of absence of room temperature DoS in valence band spectra, calculated moments and temperature dependent magnetization measurements.

cond-mat.mtrl-sci↗