arXiv subjects

Gyanti Prakash Moharana

Publications and source records attributed to Gyanti Prakash Moharana.

5 recordsLinked to original sources

arXiv2026

From spin splitting to projected mass in altermagnetic Chern matter

Altermagnetic spin splitting alone does not define Chern matter. The relevant object is the exchange mass projected onto Hall-active surface, valley, orbital or interface sectors. We formulate this projected-mass criterion for compensated magnetic topology. The resulting two-channel $(C,\mathcal{A})$ diagnostic separates hidden compensated Hall responses from additive altermagnetic quantum anomalous Hall phases in a global insulating gap. It also guides interface, thickness and materials design strategies.

cond-mat.mtrl-sci↗

arXiv2026

Griffiths-like phase, spin-phonon coupling, and exchange-bias in the disordered double perovskite GdSrCoMnO$_{6}$

We report structural, magnetic, and Raman studies of the disordered double perovskite GdSrCoMnO$_{6}$~(GSCM). DC magnetization shows a ferromagnetic transition at $T_{C} \approx 153$~K. The inverse susceptibility exhibits a downturn above $T_{C}$ and is consistent with a Griffiths-like regime extending up to $T_{G} \approx 172$~K. Raman measurements show a deviation of the phonon frequency from the anharmonic background near the magnetic-ordering region, consistent with spin-phonon coupling. AC susceptibility indicates slow magnetic dynamics below the freezing temperature $T_{f} \approx 30$~K. These results point to magnetic inhomogeneity generated by the random distribution of mixed-valence Co and Mn ions and by the resulting competition between ferromagnetic and antiferromagnetic interactions. In the low-temperature regime, an exchange-bias effect is observed up to 50~K, with an exchange-bias magnitude $|H_{EB}| = 379$~Oe at 5~K. Structural disorder therefore plays an important role in the magnetic correlations, spin dynamics, and spin-lattice response of GSCM.

cond-mat.mtrl-sci↗

arXiv2021

Interplay of Bound Magnetic Polaron and p-d exchange interaction in Co-doped 3C-SiC

Bound Magnetic Polarons (BMP) have been proposed to play an important role in doped wide band gap semiconductors. We report the experimental evidence supporting polaronic magnetism and the role of defects on it. Temperature variation of electron paramagnetic resonance study reveals that the valence state of cobalt is 2+ and its nearest environment in the system is distorted tetrahedral in nature. Room temperature ferromagnetism have been found in all the doped [Co (1, 3, 5) % doped 3C-SiC] samples. The Curie temperature, TC of the samples have been found to be above 800 K. The isothermal magnetization plots, to determine the strength of domain wall pinning were analyzed using the Jiles-Atherton Model. The temperature variation of the anisotropic constant was determined using Law of Approach to saturation (LAS), which decreases with increase in temperature. Quantitative analysis of magnetic interaction has been carried out and the result is explained by using BMP Model, which probably arises out of the exchange interaction of Co2+ ions with related (Si, C) defects.

cond-mat.mtrl-sci↗

arXiv2021

F+ Center Exchange Mechanism and Magneto Crystalline Anisotropy in Ni doped 3C-SiC

We report the experimental evidence in support of room temperature ferromagnetism in Ni doped 3C-SiC. Curie temperature is found to be > 350 K. Temperature dependent Electron paramagnetic resonance (EPR) study reveals that the valence state of Ni is 2+ and its environmental symmetry. A clear shift in both XRD and Raman peak confirms the incorporation of Ni in the host lattice. The variation in number of vacancies $V_{\mathrm{Si}}$, $V_{\mathrm{C}}$ and the number of free electron due to doping is consistent with the change in magnetization of the system. A direct correlation of ferromagnetic order (FM) with F+ centers exchange mechanism is established. The temperature variation of the anisotropic constant was determined using Law of Approach to Saturation (LAS). It was found that effective magnetic anisotropic constant decreases with increase in temperature. The EPR line width of the annealed sample increases with decrease in temperature, whereas the integrated intensity decreases with decrease in temperature. This could be due to incomplete quenching of orbital angular momentum in Si$_{x}$Ni$_{1-x}$C. In addition to this, the orbital degeneracy of fast relaxing impurity such as Ni in the cubic crystal field is not completely removed. This results in the line width decrease with increase in temperature.

cond-mat.mtrl-sci↗

arXiv2018

Role of Spin, Phonon and Plasmon Dynamics on Ferromagnetism in Cr doped 3C-SiC

The defect induced magnetism has initiated a lot of interest in field of spintronics. In this regard, SiC is a promising material because of its unique properties under extreme conditions. Hence it will be very much interesting to investigate the interaction between defects and itinerant carrier in doped SiC for spintronics application. We report the structural stability and magnetic interaction in Cr doped 3C-SiC synthesized by Thermal Plasma Technique. The EPR spectrum of undoped 3C-SiC shows a sharp resonance line corresponding to $g=2.00$ associated with the defects present in the system. Anomalous temperature evolution tendency of the relative intensity of EPR spectra can be attributed to magnetically correlated defects in the host matrix. For the first time we report the detailed quantitative analysis of X-band and Q-band EPR study in Cr doped 3C-SiC which reveals that Cr can be in multivalent state. The non monotonous variation of Longitudinal Mode (LO) of the Raman spectra has been explained based on the interaction between carriers and surface plasmon using Longitudinal optical plasmon coupling model (LOPC). The carrier density calculated by using LOPC fit with experimental data varies from $1.8\times10^{15}$ to $4.2\times10^{17}$ cm$^{-3}$. Room temperature magnetic measurements exhibit ferromagnetic behavior with non-zero coercivity for all the samples up to 7 T field. We, for the first time, show the Curie temperature to be above 760 K. Quantitative analysis of magnetic interaction validates the applicability of Bound Magnetic Polaron Model (BMP) which probably arises from the exchange interaction of Cr$^{3+}$ ions with related (Si, C) defects. The polaron density estimated from the BMP fit agrees well with the carrier density obtained from the line shape fitting of Raman spectra.

cond-mat.mtrl-sci↗