arXiv subjects

Tapas Paramanik

Publications and source records attributed to Tapas Paramanik.

5 recordsLinked to original sources

arXiv2026

Disorder-driven competing magnetic interactions and glassy magnetic behavior in quaternary Heusler alloy FeRuMnGe

In this combined experimental and theoretical study, we investigate the role of disorder in governing the magnetic ground state of the quaternary Heusler alloy FeRuMnGe. In the FeRuMnZ (Z = Ga, Si) series, chemical substitution modifies atomic ordering and electronic structure, resulting in distinct magnetic ground states. Motivated by this, we extend the series to FeRuMnGe. X-ray diffraction reveals B2-type antisite disorder, where Fe--Ru and Mn--Ge intermix. Theoretical calculations show that such disorder modifies exchange interactions, leading to competing ferromagnetic and antiferromagnetic couplings, and drives the system from half-metallic to metallic. Magnetic measurements reveal competing interactions, giving rise to a cluster-glass state coexisting with long-range magnetic order. The absence of a thermodynamic signature at $T_f$, together with ac susceptibility and relaxation measurements, supports the presence of short-range magnetic interactions and a glassy magnetic state. The compound exhibits an enhanced magnetic response below $\sim 161$ K and a maximum magnetization of $\sim 1.64~\mu_B$/f.u. at 5 T. Overall, this work establishes a direct correlation between antisite disorder, competing exchange interactions, and glassy magnetism in quaternary Heusler alloys. Combined experimental results and theoretical calculations reveal that disorder drives the system from an AFM-dominated state in FeRuMnSi to an FM-dominated state in FeRuMnGe, providing deeper insight into the role of the extent of disorder in governing the magnetic properties of QHAs.

cond-mat.str-el↗

arXiv2026

Room temperature intrinsic anomalous Hall effect in disordered half-metallic ferromagnetic quaternary Heusler alloy CoRuFeSi

Quaternary Heusler alloys offer a versatile platform for engineering magnetic and topological transport phenomena through chemical flexibility and tunable disorder. Here, we report a comprehensive experimental and theoretical investigation of the magnetic, magnetotransport, and anomalous Hall properties of the quaternary Heusler alloy CoRuFeSi. The compound crystallizes in the LiMgPdSn-type structure with significant Co--Ru antisite disorder and exhibits soft ferromagnetism with a saturation magnetization of $4.21~\mu_{\mathrm{B}}/\mathrm{f.u.}$ at low temperature and a Curie temperature well above room temperature. Hall measurements reveal a robust anomalous Hall effect persisting up to 300~K, with an anomalous Hall conductivity of $\sim 74$~S/cm that is nearly temperature independent. Scaling analysis demonstrates that the anomalous Hall response is dominated by the intrinsic Berry-curvature mechanism. First-principles calculations identify CoRuFeSi as a topologically nontrivial nodal-line semimetal in its ordered phase. Incorporation of experimentally relevant Co--Ru antisite disorder redistributes the Berry curvature and quantitatively reproduces the experimentally observed anomalous Hall conductivity, while preserving half-metallicity. These results establish CoRuFeSi as a disorder-tolerant half-metallic ferromagnet with a sizable intrinsic anomalous Hall effect at room temperature, highlighting its potential for spintronic and Hall-based device applications.

cond-mat.mtrl-sci↗

arXiv2025

Investigation of magnetic and magneto-transport properties in non-centrosymmetric antiferromagnetic semimetal GdGaSi

In this work, we investigated the magneto-transport and magnetic properties of GdGaSi, having non-centrosymmetric tetragonal structure, with space group $I4_1md$. Our theoretical results are supported by experimental studies. First-principles calculations reveal that GdGaSi is an antiferromagnetic semimetallic system, characterized by dominant electron-type charge carriers. In addition, the possible nontriviality of the crossing at the Fermi energy is consistent with isostructural LaPtSi-structured materials. The compound shows robust antiferromagnetic (AFM) ordering with a Néel temperature of 19 K, and spin-reorientation signature below $T_N$. The semimetallic nature with positive magnetoresistance ($\simeq$ 2\% at 2 K and 8 T) is observed from the magnetotransport data, having electrons as majority charge carrier, established from the Hall measurements. The strong correlation in magnetism and transport is supported by various observations, like (1) concordant transitions in $M(T)$ and $ρ(T)$ data, (2) change in the concentration and mobility of electron below $T_N$, and (3) splitting of Kohler's plots in the two branches across the transition. Thus, our findings establish GdGaSi as a material with intertwined magnetic and transport degrees of freedom, within noncentrosymmetric lattice.

cond-mat.str-el↗

arXiv2020

Engineering room-temperature multiferroicity in Bi and Fe codoped BaTiO3

Fe doping into BaTiO3, stabilizes the paraelectric hexagonal phase in place of the ferroelectric tetragonal one [P. Pal et al. Phys. Rev. B, 101, 064409 (2020)]. We show that simultaneous doping of Bi along with Fe into BaTiO3 effectively enhances the magnetoelectric (ME) multiferroic response (both ferromagnetism and ferroelectricity) at room-temperature, through careful tuning of Fe valency along with the controlled-recovery of ferroelectric-tetragonal phase. We also report systematic increase in large dielectric constant values as well as reduction in loss tangent values with relatively moderate temperature variation of dielectric constant around room-temperature with increasing Bi doping content in Ba1-xBixTi0.9Fe0.1O3 (0<x<0.1), which makes the higher Bi-Fe codoped sample (x=0.08) promising for the use as room-temperature high-k dielectric material. Interestingly, x=0.08 (Bi-Fe codoped) sample is not only found to be ferroelectrically (~20 times) and ferromagnetically (~6 times) stronger than x=0 (only Fe-doped) at room temperature, but also observed to be better insulating (larger bandgap) with indirect signatures of larger ME coupling as indicated from anomalous reduction of magnetic coercive field with decreasing temperature. Thus, room-temperature ME multiferroicity has been engineered in Bi and Fe codoped BTO (BaTiO3) compounds.

cond-mat.mtrl-sci↗

arXiv2018

Huge magnetoresistance and ultra-sharp metamagnetic transition in polycrystalline ${Sm_{0.5}Ca_{0.25}Sr_{0.25}MnO_3}$

Large magnetoresistive materials are of immense interest for a number of spintronic applications by developing high density magnetic memory devices, magnetic sensors and magnetic switches. Colossal magnetoresistance, for which resistivity changes several order of magnitude (${\sim10^4 \%}$) in an external magnetic field, occurs mainly in phase separated oxide materials, namely manganites, due to the phase competition between the ferromagnetic metallic and the antiferromagnetic insulating regions. Can one further enhance the magnetoresistance by tuning the volume fraction of the two phases? In this work, we report a huge colossal magnetoresistance along with the ultra-sharp metamagnetic transition in half doped ${Sm_{0.5}Ca_{0.25}Sr_{0.25}MnO_3}$ manganite compound by suitably tuning the volume fraction of the competing phases. The obtained magnetoresistance value at 10 K is as large as $\sim10^{13}\%$ in a 30 kOe external magnetic field and $\sim10^{15}\%$ in 90 kOe external magnetic field and is several orders of magnitude higher than any other observed magnetoresistance value reported so far. Using model Hamiltonian calculations we have shown that the inhomogeneous disorder, deduced from tunneling electron microscopy, suppresses the CE-type phase and seeds the ferromagnetic metal in an external magnetic field.

cond-mat.mtrl-sci↗