arXiv subjects

V. Kanchana

Publications and source records attributed to V. Kanchana.

At least 19 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 $\sim 1.64~μ_B$/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

Nodal-Surface and Flat-Band Driven Large Anomalous Nernst Effect in Epitaxial Ferromagnetic Weyl Metal Fe5Si3

Magnetic topological materials such as Weyl and Dirac magnets exhibit unconventional electronic properties arising from the interplay between magnetic order and band topology, leading to remarkable thermomagnetic and thermoelectric effects. Here, we investigate the ANE in epitaxial thin films of the Weyl ferromagnet candidate Fe5Si3. A pronounced transverse Nernst response exceeding approximately 1.50 microvolt per kelvin is observed at room temperature, together with a giant anomalous Nernst angle of about 0.56, indicating highly efficient conversion between thermal gradients and transverse electric fields. Beyond the anomalous contribution, a sizable topological Nernst signal of approximately 0.43 microvolt per kelvin persists above room temperature, suggesting the possible presence of real-space Berry curvature associated with nontrivial spin textures. First-principles density functional theory calculations combined with symmetry analysis reveal an unconventional electronic structure in which Weyl nodal lines, nodal surfaces, and nearly flat bands coexist near the Fermi level. This rare concurrence of multiple topological band features produces a strongly enhanced and sharply energy-dependent Berry curvature, which governs both the magnitude and temperature evolution of the observed Nernst response. The close quantitative agreement between calculated anomalous Nernst conductivity and experimental results establishes the topological electronic structure as the dominant origin of the observed thermomagnetic transport, highlighting Fe5Si3 as a chemically simple, low-cost binary topological magnet for exploring both real-space and momentum-space Berry-curvature-driven thermoelectric phenomena.

cond-mat.mtrl-sci↗

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 $4.21~μ_{\mathrm{B}}/\mathrm{f.u.}$ 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

Emergent Anomalous and Topological Hall Responses in an Epitaxial Ferromagnetic Weyl Nodal-Line metal Fe5Si3

The interplay between real and reciprocal space topology yields intrinsically linked transport phenomena in magnetic Weyl systems, wherein the broken time-reversal symmetry, strong Dzyaloshinskii-Moriya interaction, and pronounced uniaxial anisotropy stabilize the momentum-space Berry-curvature monopoles (Weyl nodes) and real-space chiral spin textures. We present a combined first-principles and experimental study of epitaxial Fe5Si3 thin films, establishing them as a magnetic Weyl nodal-line material. First-principles Density Functional Theory (DFT) calculations unambiguously reveal that Fe5Si3 hosts a topologically nontrivial electronic structure containing six pairs of Weyl nodes at or near the Fermi level, accompanied by pronounced Berry curvature at high-symmetry points of the Brillouin Zone. High-quality epitaxial films exhibit robust ferromagnetism with a Curie temperature of ~370 K and strong magneto crystalline anisotropy. The magneto transport measurements on epitaxial films reveal the corresponding Berry curvature-driven responses, including a significantly large intrinsic anomalous Hall conductivity of 504 S/cm and a high anomalous Hall angle of 5.5%, which is in good agreement with DFT calculations. A negative and non-saturating longitudinal magnetoresistance is observed, consistent with a chiral-anomaly contribution from Weyl fermions near the Fermi level (EF). Furthermore, a substantial topological Hall resistivity of 1.6 μΩ cm robust across a wide temperature range, indicating the possibility of robust chiral spin textures in the thin-film geometry. These combined theoretical and experimental results establish Fe5Si3 as a unique, low-cost, centrosymmetric magnetic Weyl nodal-line material, providing a versatile platform for exploring coupled real and reciprocal space topologies in topological spintronic applications.

cond-mat.mtrl-sci↗

arXiv2025

Crystalline electric field and large anomalous Hall effect in the candidate topological material CeGaSi

We report a comprehensive investigation of CeGaSi single crystals, including magnetic, thermodynamic, electronic, and magnetotransport properties. The powder x-ray diffraction refinement revealed that CeGaSi crystallizes in LaPtSi-type tetragonal structure with space group I41md. The electrical resistivity data show a metallic nature with a sharp drop occurring around T_m = 11 K, revealing a magnetic phase transition, which is confirmed by magnetic susceptibility and heat capacity data. The magnetic susceptibility, magnetization, and heat capacity data are analyzed through the crystalline electric field based on point charge model, suggesting that the six degenerate ground states of Ce3+ (J = 5/2) ion split into three doublets with an overall splitting energy = 288 K. The maximum negative magnetoresistance in CeGaSi for both B\parallel c and B\parallel ab field-direction is observed near T_m, it is attributed to the suppression of spin-disorder scattering by the magnetic field. The Hall resistivity data for B \parallel c and B\parallel ab show anomalous Hall signal. Our scaling analysis suggests that anomalous Hall effect in CeGaSi is dominated by the skew scattering mechanism. In addition, first-principles calculations identify CeGaSi as a nodal-line metal.

cond-mat.str-el↗

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↗

arXiv2025

Correlation stabilized ferromagnetic MnRuAs with distorted kagome lattice

We present an in-depth analysis of MnRuAs, a compound crystallizing in the P$\bar{6}$2m symmetry with a distorted kagome lattice, revealing its distinctive structural, magnetic, and electronic properties through state-of-the-art ab initio calculations. By incorporating strong correlation effects using the DFT+U approach, we demonstrate the stabilization of MnRuAs, transforming its inherent dynamical instability into a robust ferromagnetic state with significant coupling along the $c$ axis. The calculated magnon dispersion reveals a parabolic profile with a minimum at the $Γ$ point, indicative of ferromagnetic behavior. Furthermore, MnRuAs exhibits intriguing electronic properties, including quasi-one-dimensional Fermi surface and the formation of nodal sphere. Our study also delves into the electronic surface states and constant energy contours, offering valuable insights into the complex physics of this material.

cond-mat.mtrl-sci↗

arXiv2024

Electronic structure and physical properties of candidate topological material GdAgGe

We grew needle-shaped single crystals of GdAgGe, which crystallizes in a noncentrosymmetric hexagonal crystal structure with space group P$\overline{6}$2$m$ (189). The magnetic susceptibility data for $H \perp c$ reveal two pronounced antiferromagnetic transitions at $T_{N1}$ = 20 K and $T_{N2}$ = 14.5 K. The magnetic susceptibility anomalies are less prominent for $H \parallel c$. The transition at $T_{N1}$ is accompanied by a pronounced heat capacity anomaly confirming the bulk nature of the magnetic transition. Below $T_{N1}$, the electrical resistivity data follows a $T^{3/2}$ dependence. In the magnetically ordered state, GdAgGe shows positive transverse magnetoresistance, which increases with decreasing temperature and increasing field, reaching a value of $\sim$ 27% at 9 T and 10 K. The Hall resistivity data and electronic band structure calculations suggest that both the hole and electron charge carriers contribute to the transport properties. The electronic band structure displays linear band crossings near the Fermi level. The calculations reveal that GdAgGe has a nodal line with drumhead surface states coupled with a nonzero Berry phase, making it a nontrivial nodal-line semimetal.

cond-mat.str-el↗

arXiv2023

Multiple magnetic transitions, metamagnetism and large magnetoresistance in GdAuGe single crystals

We report the physical properties of GdAuGe single crystals, which were grown using Bi flux. The powder x-ray diffraction data shows that the compound crystallizes in hexagonal NdPtSb-type structure (space group P63mc). Magnetization measurements performed for field configuration H||c and H||ab show that GdAuGe orders antiferromagnetically at the Neel temperature, TN = 17.2 K. Around this temperature, heat capacity and electrical resistivity data exhibit prominent anomaly due to the antiferromagnetic (AFM) transition. In addition to an AFM phase transition, the magnetization data for H||c display the signature of field-induced metamagnetic (MM) transitions below TN. The critical field range for these transitions vary from 0.2 to 6.2 T. The critical fields for the MM transitions decrease with increasing temperature and approach zero value for temperature approaching TN. Interestingly, the magnetoresistance (MR) data (for H||c) record a sharp increase in values at the critical fields that coincide with those seen in magnetization data, tracking the presence of MM transitions. MR is positive and large (169% at 9 T and 2 K) at low temperatures. Above TN, MR becomes small and switches to negative values. Hall resistivity data reveal the predominance of hole charge carriers in the system. In addition, we observe an emergence of step-like feature in the Hall resistivity data within the field range of second MM, and a significantly large anomalous Hall conductivity of 1270 Ω-1 cm-1 at 2 K. The H-T phase diagram constructed from our detailed magnetization and magnetotransport measurements reveals multiple intricate magnetic phase transitions. The electronic and magnetic structure of GdAuGe are also thoroughly investigated using first-principles methods. The electronic band structure calculations reveal that GdAuGe is a Dirac nodal-line semimetal.

cond-mat.str-el↗

arXiv2022

Electronic structure and physical properties of EuAuAs single crystal

High-quality single crystals of EuAuAs were studied by means of powder x-ray diffraction, magnetization, magnetic susceptibility, heat capacity, electrical resistivity and magnetoresistance measurements. The compound crystallizes with a hexagonal structure of the ZrSiBe type (space group $P6_3/mmc$). It orders antiferromagnetically below 6 K due to the magnetic moments of divalent Eu ions. The electrical resistivity exhibits metallic behavior down to 40 K, followed by a sharp increase at low temperatures. The magnetotransport isotherms show a distinct metamagnetic-like transition in concert with the magnetization data. The antiferromagnetic ground state in \mbox{EuAuAs} was corroborated in the \textit{ab initio} electronic band structure calculations. Most remarkably, the calculations revealed the presence of nodal line without spin-orbit coupling and Dirac point with inclusion of spin-orbit coupling. The \textit{Z}$_2$ invariants under the effective time reversal and inversion symmetries make this system nontrivial topological material. Our findings, combined with experimental analysis, makes EuAuAs a plausible candidate for an antiferromagnetic topological nodal-line semimetal.

cond-mat.str-el↗

arXiv2020

Experimental and theoretical study of the correlated compound YbCdSn: Evidence for large magnetoresistance and mass enhancement

The unusual features of topological semimetals arise from its nontrivial band structure. The impact of strong electron correlations on the topological states remains largely unexplored in real materials. Here, we report the magnetotransport properties of YbCdSn single crystals. We found two fundamental experimental evidences of electron correlations through magnetic susceptibility and specific heat. The electron correlations in this compound lead to an intermediate valence state and enhance the effective mass of the charge carriers. This correlated state exhibits large nonsaturating magnetoresistance, low carrier density, magnetic field induced metal-semiconductor-like crossover and a plateau in resistivity at low temperatures. This compound also shows a cusp-like magnetoconductivity at low magnetic field which indicates the presence of weak antilocalization effect. Our band structure calculations of Yb$^{2+}$ state predict YbCdSn to be a topological nodal-line semimetal.

cond-mat.str-el↗

arXiv2018

Ferromagnetically correlated clusters in semi-metallic Ru2NbAl Heusler alloy

In this work, we report the structural, magnetic and electrical and thermal transport properties of the Heusler-type alloy Ru2NbAl. From the detailed analysis of magnetization data, we infer the presence of superparamagnetically interacting clusters with a Pauli paramagnetic background, while short-range ferromagnetic interaction is developed among the clusters below 5 K. The presence of this ferromagnetic interaction is confirmed through heat capacity measurements. The relatively small value of electronic contribution to specific heat, gamma (~2.7 mJ/mol-K2), as well as the linear nature of temperature dependence of Seebeck coefficient indicate a semi-metallic ground state with a pseudo-gap that is also supported by our electronic structure calculations. The activated nature of resistivity is reflected in the observed negative temperature coefficient and has its origin in the charge carrier localization due to antisite defects, inferred from magnetic measurements as well as structural analysis. Although the absolute value of thermoelectric figure of merit is rather low (ZT = 5.2*10-3) in Ru2NbAl, it is the largest among all the reported non-doped full Heusler alloys.

cond-mat.str-el↗

arXiv2017

Switching of the topologically trivial and non-trivial quantum phase transitions in compressed 1T-TiTe2: Experiments and Theory

We report the structural, vibrational and electrical transport properties up to 16 GPa of the 1T-TiTe2, a prominent layered 2D system, which is predicted to show a series of topologically trivial - nontrivial transitions under hydrostatic compression. We clearly show signatures of two iso-structural transition at 2 GPa and 4 GPa obtained from the minima in c/a ratio concomitant with the phonon linewidth anomalies of Eg and A1g modes at around the same pressures, providing strong indication of unusual electron-phonon coupling associated to these transitions. Resistivity presents nonlinear behavior over similar pressure ranges providing a strong indication of the electronic origin of these pressure driven isostructural transitions. Our data thus provide clear evidences of topological changes at A and L point of the Brillouin zone predicted to be present in the compressed 1T-TiTe2. Between 4 GPa and 8 GPa, the c/a ratio shows a plateau suggesting a transformation from an anisotropic 2D layer to a quasi 3D crystal network. First principles calculations suggest that the 2D to quasi 3D evolution without any structural phase transitions is mainly due to the increased interlayer Te-Te interactions (bridging) via the charge density overlap. In addition to the pressure dependent isostructural phase transitions, our data also evidences the occurrence of a first order structural phase transition from the trigonal (P-3m1) phase at higher pressures. We estimate the start of this structural phase transition to be 8 GPa and the symmetric of the new high-pressure phase to be monoclinic (C2/m).

cond-mat.str-el↗

arXiv2016

Electronic topological transitions in Nb$_3$X (X = Al, Ga, In, Ge and Sn) under compression investigated by first principles calculations

First principles electronic structure calculations of A-15 type Nb$_3$X (X = Al, Ga, In, Ge and Sn) compounds are performed at ambient and high pressures. Mechanical stability is confirmed in all the compounds both at ambient as well as under compression from the calculated elastic constants. We have observed four holes and two electron Fermi surfaces (FS) for all the compounds studied and FS nesting feature is observed at M and along X - $Γ$ in all the compounds. A continuous change in the FS topology is observed under pressure in all the compounds which is also reflected in the calculated elastic constants and density of states under pressure indicating the Electronic topological transitions (ETT). The ETT observed at around 21.5 GPa, 17.5 GPa in Nb$_3$Al and Nb$_3$Ga are in good agreement with the anomalies observed by the experiments.

cond-mat.mtrl-sci↗

arXiv2015

CuAlTe$_2$: A promising bulk thermoelectric material

Transport properties of Cu-based chalcopyrite materials are presented using the full potential linear augmented plane wave method and Boltzmann Semi-classical theory. All the studied compounds appear to be direct band gap semiconductors evaluated based on the Tran-Blaha modified Becke-Johnson potential. The heavy and light band combination found near the valence band maximum (VBM) drive these materials to possess good thermoelectric properties. Among the studied compounds, CuAlTe$_2$ is found to be more promising, in comparison with CuGaTe$_2$, which is reported to be an efficient thermoelectric material with appreciable figure of merit. Another interesting fact about CuAlTe$_2$ is the comparable thermoelectric properties possessed by both $n-$ type and $p-$ type carriers, which might attract good device applications and are explained in detail using the electronic structure calculations.

cond-mat.mtrl-sci↗

arXiv2015

Electronic Structure, Transport and Phonons of SrAg$Ch$F ($Ch$=S, Se, Te): Bulk Superlattice Thermoelectrics

We report calculations of the electronic structure, vibrational properties and transport for the p-type semiconductors, SrAg$Ch$F ($Ch$=S, Se and Te). We find soft phonons with low frequency optical branches intersecting the acoustic modes below 50 $cm^{-1}$, indicative of a material with low thermal conductivity. The bands at and near the valence band maxima are highly two dimensional, which leads to high thermopowers even at high carrier concentrations, which is a combination that suggests good thermoelectric performance. These materials may be regarded as bulk realizations of superlattice thermoelectrics.

cond-mat.mtrl-sci↗

arXiv2014

High Pressure Structural Stability, and Optical Properties of Scheelite type ZrGeO$_4$ and HfGeO$_4$ X-ray Phosphor Hosts

\emph{Ab-initio} calculations were performed on the scheelite type MGeO$_4$ (M = Hf, and Zr) compounds which find wide range of applications such as in x-ray imaging. We have studied the high pressure structural stability, elastic constants, electronic structure and optical properties of these compounds through density functional theory calculations. Two different density functional approaches namely plane wave pseudopotential method (PW-PP) and full potential linearized augmented plane wave method (FP-LAPW) were used for the present study. The ground state structural and vibrational properties are calculated and found to be in good agreement with experimental data. The compressibility of Zr and Hf germanates is found to be anisotropic as the a-axis is less compressible over c-axis due to the presence of Ge-O bonds along a-axis which is further confirmed from the ordering of the elastic constants that follows C$_{11}$ $>$ C$_{33}$. The electronic structure of the compounds has been calculated through recently developed Tran Blaha-modified Becke Johnson potential. The calculated electronic structure shows that the compounds are insulators with a gap of 5.39 eV for ZrGeO$_4$ and 6.25 eV for HfGeO$_4$ respectively. Optical anisotropy of these compounds are revealed from the computed optical properties such as complex dielectric function, refractive index, and absorption coefficient. In addition, it is observed that Ti doped ZrGeO$_4$ and HfGeO$_4$ turns out to be a good phosphor as the pristine compounds have the energy gap greater than the visible range upon Ti doping bandgap reduces as a result emission spectra occurs in the visible region and is well explained in the present study.

cond-mat.mtrl-sci↗

arXiv2014

Thermoelectric properties of marcasite and pyrite FeX$_2$(X=Se,Te): A first principle study

Electronic structure and thermoelectric properties of marcasite (m) and synthetic pyrite (p) phases of FeX$_2$ (X=Se,Te) have been investigated using first principles density functional theory and Boltzmann transport equation. The plane wave pseudopotential approximation was used to study the structural properties and full-potential linear augmented plane wave method was used to obtain the electronic structure and thermoelectric properties (thermopower and power factor scaled by relaxation time). From total energy calculations we find that m-FeSe$_2$ and m-FeTe$_2$ are stable at ambient conditions and no structural transition from marcasite to pyrite is seen under the application of hydrostatic pressure. The calculated ground state structural properties agree quite well with available experiments. From the calculated thermoelectric properties, we find that both m and p forms are good candidates for thermoelectric applications. However, hole doped m-FeSe$_2$ appears to be the best among all the four systems.

cond-mat.mtrl-sci↗