arXiv subjects

D. Samal

Publications and source records attributed to D. Samal.

15 recordsLinked to original sources

arXiv2026

Interfacial control of magnetism and electron transport in nonisostructural SrRuO$_3$/SrCuO$_2$ heterostructure

Heterointerfaces between structurally dissimilar oxides provide a platform to exploit the interfacial mismatch in the lattice and electronic degrees of freedom to realize emergent functionalities and tunable physical properties with potential applications in oxide electronics. Here, we investigate the magnetic and electronic transport properties of symmetry-mismatched SrRuO$_3$ (SRO)/SrCuO$_2$ (SCO) heterostructure, in which a 4-nm-thick itinerant ferromagnetic metal SRO is interfaced with a planar-type antiferromagnetic insulator SCO, in comparison with a reference SRO (4 nm) film. While both the bare SRO and SRO/SCO bilayer exhibit perpendicular magnetic anisotropy (PMA), the SRO/SCO bilayer shows a pronounced enhancement in the saturation magnetization (M$_S$ $\approx$ 2.7 $\mu_B$/Ru) and effective anisotropy constant (K$_{\mathrm{eff}}$ $\approx$ 2.13 $\times$ 10$^6$ erg/cc) relative to the bare SRO film (M$_S$ $\approx$ 1.3 $\mu_B$/Ru and K$_{\mathrm{eff}}$ $\approx$ 5.25 $\times$ 10$^5$ erg/cc). Interestingly, the low-temperature resistivity upturn below 5 K arising from disorder-induced quantum corrections in bare SRO is strongly suppressed in SRO/SCO, and it exhibits Fermi-liquid-like transport ($\rho \propto T^2$) down to 2 K. Analysis of the anomalous Hall effect (AHE) reveals dominant intrinsic Berry-curvature driven electron transport in both samples, with enhanced intrinsic and skew-scattering contributions in the SRO/SCO bilayer, indicating the critical role of the interface in modifying the electronic band structure near the Fermi level. Our results demonstrate that the interface acts as an effective control knob, concurrently enhancing the magnetization, PMA, and intrinsic scattering contribution to the AHE in the SRO/SCO heterostructure, while suppressing the disorder-driven quantum corrections to transport behavior observed in the bare SRO film.

cond-mat.str-el↗

arXiv2026

Probing Interfacial Magnetic Anisotropy in \texorpdfstring{CoV$_{2}$O$_{4}$}{CoV2O4} using Spin Hall Magnetoresistance

Spin Hall magnetoresistance (SMR) has emerged as a powerful probe for investigating interfacial spin transport and magnetic anisotropy in complex oxide heterostructures. In this work, we investigate the interfacial magnetic anisotropy in Pt/CVO through angle-dependent magnetotransport measurements. Unlike the bulk-sensitive magnetic measurements on both strained CVO and Pt/CVO films, which exhibit a ferrimagnetic transition at $T_{C} \approx 150$ K accompanied by out-of-plane anisotropy that reorients toward in-plane anisotropy below 90 K, SMR reveals a distinct interfacial magnetic anisotropy. The rotational scans of the in-plane transverse SMR at 20 K exhibit substantial hysteresis about [100], while no hysteresis is observed along [110] and [1$\bar{1}$0], indicating a biaxial anisotropy with easy axes along [110] and [1$\bar{1}$0]. Furthermore, the absence of sharp discontinuities in both the in-plane longitudinal and transverse SMR, together with pronounced discontinuities near the in-plane [010] direction during out-of-plane rotation, strongly indicates the presence of in-plane anisotropy. This behavior persists up to 120 K. The discrepancy between the bulk-sensitive magnetic measurements and the SMR response suggests that the Pt/CVO interface retains a magnetic anisotropy distinct from the bulk, highlighting the interfacial sensitivity of SMR. Additionally, the spin mixing conductance is found to be of the order of $10^{14}$ $\Omega^{-1}\mathrm{m}^{-2}$, comparable to other oxide-based spintronic systems. These findings highlight the crucial role of interfacial effects in spin transport and establish Pt/CVO as a promising platform for spintronic applications.

cond-mat.str-el↗

arXiv2026

Interface and Strain Control of Emergent Weyl Semimetallic Phase in SrNbO$_{3}$/LaFeO$_{3}$ Heterostructures

Realizing correlated topological semimetallic phases in bulk transition-metal oxides remains challenging due to rigid lattice symmetry, correlation-induced gap opening, and limited structural tunability. However, complex-oxide thin films and heterostructures provide a powerful platform to stabilize topological phases by tailoring the requisite lattice symmetry through strain control and interface design. In this study, we demonstrate the emergence of Weyl-like electronic states and associated chiral transport in SrNbO$_3$ (SNO)/LaFeO$_3$ (LFO) bilayers. Transport measurements reveal signatures consistent with nontrivial topology, including large non-saturating MR, a nonlinear Hall response, and a chiral anomaly like feature in longitudinal magnetotransport under parallel electric and magnetic fields ($\mathbf{B} \parallel \mathbf{I}$). In addition, we observe a \textcolor{black}{signature} of anomalous Hall contribution, likely arising from \textcolor{black}{proximity effect induced by LFO layers at the interface}. First-principles calculations reveal an $a^0a^0c^-$ rotation pattern of the NbO$_6$ octahedra, together with interfacial lattice distortions in the SNO layer that drive the emergence of a twofold degenerate Weyl semimetallic phase protected by screw axis lattice symmetry. This is further confirmed by Berry curvature calculations, which show opposite sign Berry curvature peaks for the upper and lower band characteristic of a Weyl node. Our combined experimental and theoretical results highlight the critical role of strain and interfacial octahedral distortions in stabilizing Weyl phase in transition metal based perovskite bilayer.

cond-mat.str-el↗

arXiv2025

Magnetic order and spin dynamics across the ferromagnetic quantum critical point in Ni\boldmath{$_{1-x}$}Mo\boldmath{$_{x}$}

Realizing a quantum critical point (QCP) in clean ferromagnetic (FM) metals has remained elusive due to the coupling of magnetization to the electronic soft modes that drive the transition to be of first order. However, by introducing a suitable amount of quenched disorder, one can still establish a QCP in ferromagnets. In this study, we ascertain that the itinerant ferromagnet Ni$_{1-x}$Mo$_{x}$ exhibits a FM QCP at a critical doping of $x_c \simeq 0.125$. Through magnetization and muon-spin relaxation measurements, we demonstrate that the FM ordering temperature is suppressed continuously to zero at $x_c$, while the magnetic volume fraction remains $100\%$ up to $x_c$, indicating a second-order phase transition. The QCP is accompanied by a non-Fermi liquid behavior, as evidenced by the logarithmic divergence of the specific heat and the linear temperature dependence of the low-temperature resistivity. Our findings reveal a minimal effect of disorder on the critical spin dynamics of Ni$_{1-x}$Mo$_{x}$ at $x_c$, highlighting it as one of the rare systems to exhibit a clean FM QCP.

cond-mat.str-el↗

arXiv2024

Evolution of ferrimagnetism against Griffiths singularity in Calcium Ruthenate

The magnetism in the correlated metal CaRuO$_3$ is enigmatic as it is poised near a triple point among the ferromagnetic, antiferromagnetic, and paramagnetic ground states. Here we report a detailed work on structural, spectroscopic, magnetic, and transport properties in CaRu$_{1-x}$Cr$_x$O$_3$. We find that Cr doping reduces the orthorhombicity in CaRuO$_3$. Surprisingly, a tiny (x = 0.01) amount of Cr-doping drives the magnetic ground state from \enquote{paramagnetic-like} to ferrimagnetic. Slightly higher Cr-doping (x = 0.05) results formation of magnetic clusters which gives rise to Griffiths singularity and power law divergence in magnetic susceptibility. The magnetism in CaRu$_{1-x}$Cr$_x$O$_3$ is explained in terms of \enquote{seven atom} ferrimagnetic clusters. Electrical transport shows a gradual evolution of a non-metallic state upon Cr-doping. In particular, for x $\geq$ 0.1, the temperature-dependent resistivity follows Mott-VRH conduction. The XPS study also supports significant role of disorder and electron correlation which effectively reduces the itinerant character of electrons. Finally, a new T-x phase diagram is constructed depicting the evolution of electronic and magnetic state in CaRu$_{1-x}$Cr$_x$O$_3$.

cond-mat.str-el↗

arXiv2023

Electronic Transport and Fermi Surface Topology of Zintl Phase Compound SrZn2Ge2

We report a comprehensive study on the electronic transport properties of SrZn2Ge2 single crystals. The electrical resistivity of the compound exhibits metallic behavior, following a T^2 dependence below 35 K, consistent with the Fermi liquid behavior. However, a notable deviation is observed from this behavior at lower temperatures as a pronounced resistivity plateau emerges below 10 K. This plateau is remarkably robust, and persists under the magnetic fields of up to 10 T. Both the transverse and longitudinal magnetoresistance exhibit a crossover at critical field B* from weak-field quadratic-like to high-field unsaturated linear field dependence at low temperatures (T \leq 50 K). Possible sources of linear magnetoresistance are discussed based on the Fermi surface topology, classical and quantum transport models. The Hall resistivity data establish SrZn2Ge2 as a multiband system with contributions from both the electrons and holes. The Hall coefficient is observed to decrease with increasing temperature and magnetic field, changing its sign from positive to negative. The negative Hall coefficient observed at low temperatures in high fields and at high temperatures over the entire field range suggests that the highly mobile electron charge carriers dominate the electronic transport. Our first-principles calculations show that nontrivial topological surface states exist in SrZn2Ge2 within the bulk gap along the Gamma-M path. Notably, these surface states extend from the valence to conduction band with their number varying based on the Sr and Ge termination plane. The Fermi surface of the compound exhibits a distinct tetragonal petal-like structure, with one open and several closed surfaces. Overall, these findings offer crucial insights into the mechanisms underlying the electronic transport of the compound.

cond-mat.str-el↗

arXiv2023

Crystal structure and magnetic properties of spin-$1/2$ frustrated two-leg ladder compounds (C$_4$H$_{14}$N$_2$)Cu$_2X_6$ ($X$= Cl and Br)

We have successfully synthesized single crystals, solved the crystal structure, and studied the magnetic properties of a new family of copper halides (C$_4$H$_{14}$N$_2$)Cu$_2X_6$ ($X$= Cl, Br). These compounds crystallize in an orthorhombic crystal structure with space group $Pnma$. The crystal structure features Cu$^{2+}$ dimers arranged parallel to each other that makes a zig-zag two-leg ladder-like structure. Further, there exists a diagonal interaction between two adjacent dimers which generates inter-dimer frustration. Both the compounds manifest a singlet ground state with a large gap in the excitation spectrum. Magnetic susceptibility is analyzed in terms of both interacting spin-$1/2$ dimer and two-leg ladder models followed by exact diagonalization calculations. Our theoretical calculations in conjunction with the experimental magnetic susceptibility establish that the spin-lattice can be described well by a frustrated two-leg ladder model with strong rung coupling ($J_0/k_{\rm B} \simeq 116$ K and 300 K), weak leg coupling ($J^{\prime\prime}/k_{\rm B} \simeq 18.6$ K and 105 K), and equally weak diagonal coupling ($J^{\prime }/k_{\rm B} \simeq 23.2$ K and 90 K) for Cl and Br compounds, respectively. These exchange couplings set the critical fields very high, making them experimentally inaccessible. The correlation function decays exponentially as expected for a gapped spin system. The structural aspects of both the compounds are correlated with their magnetic properties. The calculation of entanglement witness divulges strong entanglement in both the compounds which persists upto high temperatures, even beyond 370~K for the Br compound.

cond-mat.mtrl-sci↗

arXiv2022

Multi-band character revealed from Weak-antilocalization effect in Platinum thin films

Platinum (Pt) has been very much used for spin-charge conversion in spintronics research due to it's large intrinsic spin-orbit interaction. Magnetoconductance originated from weak-antilocalization effect in quantum interference regime is used as a powerful tool to obtain the microscopic information of spin-orbit interaction and coherence phase breaking scattering process among itinerant electrons. To acquire the knowledge of different types of scattering processes, we have performed magnetoconductance study on Pt thin films which manifests multi-band (multi-channel) conduction. An extensive analysis of quantum interference originated weak-antilocalization effect reveals the existence of strong (weak) inter-band scattering between two similar (different) orbitals. Coherence phase breaking lengths ($l_{\phi}$) and their temperature dependence are found to be significantly different for these two conducting bands. The observed effects are consistent with theoretical predication that there exist three Fermi-sheets with one $s$ and two $d$ orbital character. This study provides the evidence of two independent non-similar conducting channels and presence of anisotropic spin-orbit interaction along with $e$-$e$ correlation in Pt thin films.

cond-mat.str-el↗

arXiv2021

Damping in yttrium iron garnet film with an interface

We report strong damping enhancement in a 200 nm thick yttrium iron garnet (YIG) film due to spin inhomogeneity at the interface. The growth-induced thin interfacial gadolinium iron garnet (GdIG) layer antiferromagnetically (AFM) exchange couples with the rest of the YIG layer. The out-of-plane angular variation of ferromagnetic resonance (FMR) linewidth $\Delta H$ reflects a large inhomogeneous distribution of effective magnetization $\Delta 4 \pi M_{eff}$ due to the presence of an exchange springlike moments arrangement in YIG. We probe the spin inhomogeneity at the YIG-GdIG interface by performing an in-plane angular variation of resonance field $H_{r}$, leading to a unidirectional feature. The large extrinsic $\Delta 4\pi M_{eff}$ contribution, apart from the inherent intrinsic Gilbert contribution, manifests enhanced precessional damping in YIG film.

cond-mat.mtrl-sci↗

arXiv2019

Unusual Valence State in the Antiperovskites Sr$_3$SnO and Sr$_3$PbO Revealed by X-ray Photoelectron Spectroscopy

The class of antiperovskite compounds $A_3B$O ($A$ = Ca, Sr, Ba; $B$ = Sn, Pb) has attracted interest as a candidate 3D Dirac system with topological surface states protected by crystal symmetry. A key factor underlying the rich electronic structure of $A_3B$O is the unusual valence state of $B$, i.e., a formal oxidation state of $-4$. Practically, it is not obvious whether anionic $B$ can be stabilized in thin films, due to its unusual chemistry, as well as the polar surface of $A_3B$O, which may render the growth-front surface unstable. We report X-ray photoelectron spectroscopy (XPS) measurements of single-crystalline films of Sr$_3$SnO and Sr$_3$PbO grown by molecular beam epitaxy (MBE). We observe shifts in the core-level binding energies that originate from anionic Sn and Pb, consistent with density functional theory (DFT) calculations. Near the surface, we observe additional signatures of neutral or cationic Sn and Pb, which may point to an electronic or atomic reconstruction with possible impact on putative topological surface states.

cond-mat.mes-hall↗

arXiv2019

Evidence for weak antilocalization-weak localization crossover and metal-insulator transition in CaCu$_{3}$Ru$_{4}$O$_{12}$ thin films

Artificial confinement of electrons by tailoring the layer thickness has turned out to be a powerful tool to harness control over competing phases in nano-layers of complex oxides. We investigate the effect of dimensionality on transport properties of $d$-electron based heavy-fermion metal CaCu$_{3}$Ru$_{4}$O$_{12}$. Transport behavior evolves from metallic to localized regime upon reducing thickness and a metal insulator transition is observed below 3 nm film thickness for which sheet resistance crosses $h/e^{2} \sim 25~$k$\Omega$, the quantum resistance in 2D. Magnetotransport study reveals a strong interplay between inelastic and spin-orbit scattering lengths upon reducing thickness, which results in weak antilocalization (WAL) to weak localization (WL) crossover in magnetoconductance.

cond-mat.str-el↗

arXiv2018

The effect of Sn intercalation on the superconducting properties of 2H-NbSe2

2H-NbSe2 is known to be an archetype layered transitional metal dichalcogenide superconductor with a superconducting transition temperature of 7.3 K.In this article, we investigate the influence of Sn intercalation on superconducting properties of 2H-NbSe2. Sn being nonmagnetic and having no outer shell d-electrons unlike transition metals, one naively would presume that its effect on superconducting properties will be very marginal. However, our magnetic and transport studies reveal a significant reduction of both superconducting transition temperature and upper critical field [Tc and BC2 (0)] upon Sn intercalation. With a mere 4 mole% Sn intercalation, it is observed that Tc and BC2 (0) get suppressed by ~ 3.5 K and 3 T, respectively. Werthamer-Helfand-Hohenberg (WHH) analysis of magneto-transport data is performed to estimate BC2 (0). From the low temperature Raman scattering data in the normal phase of intercalated NbSe2, it is inferred that the suppression of superconductivity cannot be ascribed to strengthening of charge density wave (CDW)ordering. The effects such as electron-doping induced Fermi surface change and/or disorder scattering upon intercalation are speculated to be at play for the observed phenomena.

cond-mat.supr-con↗

arXiv2018

Unconventional exchange bias coupling at perovskite/brownmillerite interface in spontaneously stabilized SrCoO3-{\delta}/SrCoO2.5 bi-layer

Interface effect in complex oxide thin film heterostructures lies at the vanguard of current research to design technologically relevant functionality and explore emergent physical phenomena. While most of the previous works focus on the perovskite/perovskite heterostructures, the study on perovskite/brownmillerite interfaces remain at its infancy. Here, we investigate spontaneously stabilized perovskite-ferromagnet (SrCoO3-{\delta})/brownmillertite-antiferromagnet (SrCoO2.5) bi-layer with TN > TC and discover an unconventional interfacial magnetic exchange bias effect. From magnetometry investigations, it is rationalized that the observed effect stems from the interfacial ferromagnet/antiferromagnet coupling. The possibility for coupled ferromagnet/spinglass interface engendering such effect is ruled out. Strikingly, a finite coercive field persists in the paramagnetic state of SrCoO3-{\delta} whereas the exchange bias field vanishes at TC. We conjecture the observed effect to be due to the effective external quenched staggered field provided by the antiferromagtic layer for the ferromagnetic spins at the interface. Our results not only unveil a new paradigm to tailor the interfacial magnetic properties in oxide heterostructures without altering the cations at the interface, but also provide a purview to delve into the fundamental aspects of exchange bias in such unusual systems paving a big step forward in thin film magnetism.

cond-mat.mtrl-sci↗

arXiv2018

Robust weak antilocalization due to spin-orbital entanglement in Dirac material Sr$_3$SnO

The presence of both inversion ($P$) and time-reversal ($T$) symmetries in solids leads to a well-known double degeneracy of the electronic bands (Kramers degeneracy). When the degeneracy is lifted, spin textures can be directly observed in momentum space, as in topological insulators or in strong Rashba materials. The existence of spin textures with Kramers degeneracy, however, is very difficult to observe directly. Here, we use quantum interference measurements combined with first-principle band structure calculations to provide evidence for the existence of hidden entanglement between spin and momentum in the antiperovskite-type 3D Dirac material Sr$_3$SnO. We find robust weak antilocalization (WAL) independent of the position of $E_\mathrm{F}$. The observed WAL signal at low doping is fitted using a single interference channel, which implies that the different Dirac valleys are mixed by disorder. Notably, this mixing does not suppress WAL, suggesting contrasting interference physics compared to graphene. We identify scattering among axially spin-momentum locked states as a key process that leads to a spin-orbital entanglement, giving rise to robust WAL. Our work sheds light on the subtle role of spin and pseudospin, when both could contribute to the same quantum effect.

cond-mat.mes-hall↗

arXiv2016

Quenched Magnon excitations by oxygen sublattice reconstruction in (SrCuO$_2$)$_n$/(SrTiO$_3$)$_2$ superlattices

The recently discovered structural reconstruction in the cuprate superlattice (SrCuO$_2$)$_n$/(SrTiO$_3$)$_2$ has been investigated across the critical value of $n=5$ using resonant inelastic x-ray scattering (RIXS). We find that at the critical value of $n$, the cuprate layer remains largely in the bulk-like two-dimensional structure with a minority of Cu plaquettes being reconstructed. The partial reconstruction leads to quenching of the magnons starting at the $\Gamma$-point due to the minority plaquettes acting as scattering points. Although comparable in relative abundance, the doped charge impurities in electron-doped cuprate superconductors do not show this quenching of magnetic excitations.

cond-mat.str-el↗