arXiv subjects

Soham Manni

Publications and source records attributed to Soham Manni.

14 recordsLinked to original sources

arXiv2025

Probing the magnetic ground state and magnetoelastic coupling in double perovskite ruthenate: Ca2ScRuO6

Ruthenates, materials with a single magnetic Ruthenium (Ru) atom, often display an exotic array of ground states ranging from superconductivity to altermagnetism. In this work, we investigated the magnetic ground state of a least explored member of the 4d3 double perovskite ruthenate series A2ScRuO6 (A = Ca, Sr, Ba): Ca2ScRuO6. Interestingly, temperature-dependent bulk susceptibility curve shows ferrimagnetic-like behaviour above the magnetic ordering at around 40 K, which were corroborated by the identification of the mixed valence states, Ru5+ and Ru4+ via X-ray absorption spectroscopy. Structural analysis further revealed atomic-site exchange between the Ru and Sc sites, which results in the Ru mixed valence states. Neutron powder diffraction measurements detected the presence of magnetic Bragg peaks at a low temperature near 4 K and a moderate magnetoelastic coupling near the ordering temperature of 40 K. However, the corresponding symmetry analysis shows a weak Type I antiferromagnetic ground state with a reduced magnetic moment of 1.1{\mu}B/Ru atom. Our findings establish an unusual magnetic ground state in the Mott insulating Ca2ScRuO6, where a long range ordered antiferromagnet coexists with small magnetic clusters, which manifests a ferrimagnetic-like high temperature inverse magnetic susceptibility. This system presents a unique platform to study long-range magnetic order in the presence of antisite disorder.

cond-mat.str-el↗

arXiv2025

Disorder mediated fully compensated ferrimagnetic spin-gapless semiconducting behaviour in Cr3Al Heusler alloy

Spin-gapless semiconductors (SGSs) that simultaneously host fully compensated ferrimagnetism are highly sought for energy-efficient and stray-field-free spintronic technologies, yet their realization in chemically disordered systems has remained elusive. Here, we demonstrate that the binary Heusler alloy Cr3Al despite adopting a fully A2-disordered structure exhibits a rare coexistence of SGS transport and a fully compensated ferrimagnetic (FCF) ground state. Single-crystalline and polycrystalline Cr3Al samples were synthesized, and comprehensive structural analyses using single crystal XRD, synchrotron powder XRD, and neutron powder diffraction reveal complete Cr/Al site mixing. Remarkably, this chemical disorder does not disrupt magnetic order; instead, magnetization, X-ray magnetic circular dichroism (XMCD), and temperature-dependent neutron diffraction establish a robust compensated ferrimagnetic state with a vanishingly small ordered moment of 0.1(1) muB/f.u and a high Curie temperature of 773(2) K. Electrical and thermal transport measurements uncover clear SGS characteristics, including weak temperature-dependent conductivity, very low Seebeck coefficients, and electron-hole compensated transport. Hall measurements show unusual temperature-dependent carrier concentrations consistent with disorder-modified electronic states. First-principles calculations on an A2-disordered SQS structure reproduce the experimentally observed negligibly small magnetization (0.0072 muB/f.u) and reveal a vanishing spin-up band gap unambiguously supporting SGS behavior driven by chemical disorder. Our results identify Cr3Al as the first experimentally verified A2-disordered Heusler alloy exhibiting both fully compensated ferrimagnetism and spin-gapless semiconducting transport, positioning it as a robust and disorder-tolerant platform for next-generation, high-temperature spintronic devices.

cond-mat.mtrl-sci↗

arXiv2025

Cavity based sensing of antiferromagnetic canting and nonzero-momentum spin waves in a van der Waals cavity-magnon-polariton system

Cavity-magnon-polaritons are hybrid excitations from the interaction between cavity photons and magnons, the quanta of collective spin oscillations. Along with the tunability of the magnon-photon coupling strength, fast information transfer and conversion speed are desired in hybrid devices. This can be achieved utilizing the propagating nature of spin waves with non-zero momentum for their ultra-fast time dynamics and reduced ohmic dissipation. Antiferromagnets are particularly interesting as hosts for magnons since stray-field interactions are minimized, and they support multiple modes with distinctive magnetic-field behavior across the phase diagram. CrCl3 is a van der Waals antiferromagnet having a strong easy-plane anisotropy and a weak in-plane easy-axis anisotropy. Despite some magnetic resonance studies, the impact of magnetic reorientation of spins in CrCl3 on cavity-magnon-polariton interaction strength as a function of magnetic field remains largely unexplored. In this study, we investigate the coupling between magnons in CrCl3 and photons in a coplanar waveguide resonator as a function of magnetic field. In particular, we find that the magnon-photon coupling strength varies nonmonotonically and distinctly with the magnetic field for both acoustic and optical magnons, enabling tuning of the coupling strength with an external magnetic field as a knob. We find the signature of spin-flop transition in two harmonics of the cavity due to a stronger dispersive coupling between optical magnons and cavity photons at lower fields. Additionally, we find standing modes formed by spin waves with nonzero momentum associated with the two hybrid magnons when the external field is applied at an angle with the crystal plane. These modes do not undergo substantial coupling with the cavity mode unlike the antiferromagnetic modes and can be used as low-loss propagation channels in hybrid devices.

cond-mat.mes-hall↗

arXiv2025

Electron doping in single crystalline BaBiO$_3$: BaBiO$_{3-x}$F$_{x}$

Topological insulators are a new class of insulators with conducting surface state. Most of the topological insulators are chalcogenides, where a tiny amount of chalcogen vacancy destroys the predicted bulk insulating state and results in a metallic or semimetallic bulk electrical transport. BaBiO$_3$ (BBO) is an interesting large bandgap (0.7 eV) insulator that upon hole doping becomes a superconductor and is theoretically predicted to show a topological insulating state under electron doping. We have explored electron doping through the chemical substitution of fluorine atoms at the oxygen site. The single crystals of BBO and fluorine doped BBO were synthesized via a one-step solid-state technique. The single crystals of pure BBO and 10 % F -doped BBO (BaBiO$_{2.7}$F$_{0.3}$) are chemically single-phase samples and crystallize in monoclinic I2/m crystal structure. The core level and valence band X-ray photoelectron spectra confirm electron doping in the 10% fluorine-doped BBO. 20 % F-doped BBO appears to be a multiphase sample, confirmed by back-scattered electron (BSE) imaging and X-ray diffraction. This article reports on the successful growth of pure and F-doped BBO using a one-step solid-state technique and discusses the effect of F-doping on structural and electronic properties.

cond-mat.str-el↗

arXiv2025

Investigation of competing magnetic orders and the associated spin-phonon coupling effect in quasi-2D Cr1+xTe2 (x = 0.22) single crystal

Single crystals of quasi-2D chromium telluride system represented by Cr1+xTe2 (x = 0.22), which crystallizes in the trigonal structure with the c-axis as the growth direction, are synthesized by the flux method. The magnetization measurements revealed the coexistence and competition between ferromagnetic and antiferromagnetic exchange interactions due to the presence of the intercalated Cr-layers. A series of diverse magnetic transitions is exhibited by the crystal. While cooling the crystal, it undergoes a paramagnetic to antiferromagnetic transition at 190 K, followed by a transition into a ferromagnetic state at around 160 K, and a spin-canting at a lower temperature of 75 K. A possible lack of inversion symmetry in the crystal structure, along with the observance of an unusual jump and loop opening in the isothermal magnetization suggests that the crystals Cr1+xTe2 (x = 0.22) may host skyrmions. Furthermore, concomitant to their magnetic transitions, anomalies were observed in the derived Breit-Wigner-Fano fit parameters obtained from the asymmetric temperature-dependent Raman spectra, evidencing a strong spin-phonon coupling effect, intrinsic to the grown crystals. A strong perpendicular magnetic anisotropy along with the robust spin-phonon coupling, makes the system a promising candidate for prospective spintronics applications.

cond-mat.str-el↗

arXiv2024

Electronic and magnetic ground state of 4$d^3$ double perovskite ruthenates A$_2$LaRuO$_6$ (A $=$ Ca, Sr, Ba)

4$d$ transition metal oxide (TMO) offers an intriguing puzzle for their electronic and magnetic ground state. They are in the cross-over regime of strong spin orbit interaction (SOI) and electron-electron correlation ($U$) with quenched orbital angular momentum. Our work unravels the electronic and magnetic ground state of the less investigated 4$d^{3}$ double perovskite ruthenates A$_{2}$LaRuO$_6$ (A = Ca, Ba). The negligible effect of SOI is evident from the bulk magnetic, specific heat measurements and density functional theory (DFT) calculations, indicating a classical spin-only magnetic ground state (${S}$ = 3/2) for the materials. Magnetization measurements show that both materials have long range antiferromagnetic order with high degree of magnetic frustration ($f$ $\approx$13 -15). Interestingly, a near $T^2$- behavior is observed in low-$T$ magnetic heat capacity measurement, indicating the presence of low-dimensional spin-wave exciation and magnetic frustration in both materials. The temperature dependent resistivity measurements and electronic band structure calculations confirm a conventional Mott insulating ground state in these two systems. Moreover, our experimental investigation and DFT calculations highlight the reason for the nonexistence of Sr$_2$LaRuO$_6$.

cond-mat.str-el↗

arXiv2022

Observation of superconductivity in the noncentrosymmetric nodal chain semimetal Ba5In4Bi5

The combination with superconductivity and topological nontrivial band structure provides a promising route towards novel quantum states such as topological superconductivity. Here, we report the first observation of superconductivity (4.1 K) in Ba5In4Bi5 single crystal, a noncentrosymmetric topological semimetal featuring nodal chain loops at the high-symmetry points R and X. The magnetization, resistivity, and specific heat capacity measurements reveal that Ba5In4Bi5 is a moderately coupled type-II Bardeen-Cooper-Schrieffer superconductor. Bulk superconductivity is suggested from the magnetic susceptibility and specific heat measurements. The results show that Ba5In4Bi5 provides a new platform for exploring the relationship of superconductivity and topological nontrivial band topology.

cond-mat.supr-con↗

arXiv2021

Coplanar cavity for strong coupling between photons and magnons in van der Waals antiferromagnet

We investigate the performance of niobium nitride superconducting coplanar waveguide resonators towards hybrid quantum devices with magnon-photon coupling. We find internal quality factors ~ 20000 at 20 mK base temperature, in zero magnetic field. We find that by reducing film thickness below 100 nm internal quality factor greater than 1000 can be maintained up to parallel magnetic field of ~ 1 T and perpendicular magnetic field of ~ 100 mT. We further demonstrate strong coupling of microwave photons in these resonators, with magnons in chromium trichloride, a van der Waals antiferromagnet, which shows that these cavities serve as a good platform for studying magnon-photon coupling in 2D magnonics based hybrid quantum systems. We demonstrate strong magnon-photon coupling for both optical and acoustic magnon modes of an antiferromagnet.

cond-mat.mes-hall↗

arXiv2020

Evidence of standing spin-waves in a van der Waals magnetic material

Spin-waves have been studied for data storage, communication and logic circuits in the field of spintronics based on their potential to substitute electrons. Recent discovery of magnetism in two-dimensional (2D) systems such as monolayer CrI$_3$ and Cr$_2$Ge$_2$Te$_6$ has led to a renewed interest in such applications of magnetism in the 2D limit. Here we present direct evidence of standing spin-waves along with the uniform precessional resonance modes in van der Waals magnetic material, CrCl$_3$. Our experiment is the first direct observation of standing spin-wave modes, set up across a thickness of 20 $μ$m, in a van der Waals material. We detect standing spin-waves in the vicinity of both, optical and acoustic, branches of the antiferromagnetic resonance. We also observe magnon-magnon coupling, softening of resonance modes with temperature and extract the evolution of interlayer exchange field as a function of temperature.

cond-mat.mtrl-sci↗

arXiv2018

Effect of pressure on the physical properties of the superconductor NiBi3

We present an experimental study of the superconducting properties of NiBi3 as a function of pressure by means of resistivity and magnetization measurements and combine our results with DFT calculations of the band structure under pressure. We find a moderate suppression of the critical temperature Tc from ~ 4.1K to ~ 3K by pressures up to 2GPa. By taking into account the change of the band structure as a function of pressure, we argue that the decrease in Tc is consistent with conventional, electron-phonon-mediated BCS-type superconductivity.

cond-mat.supr-con↗

arXiv2018

Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling

Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises ultrathin insulating multiferroics, spin liquids, and ferromagnets, but new characterization methods are required to unlock their potential. Here, we report tunneling through the layered magnetic insulator CrI3 as a function of temperature and applied magnetic field. We electrically detect the magnetic ground state and inter-layer coupling and observe a field-induced metamagnetic transition. The metamagnetic transition results in magnetoresistances of 95%, 300%, and 550% for bilayer, trilayer, and tetralayer CrI3 barriers, respectively. We further measure inelastic tunneling spectra for our junctions, unveiling a rich spectrum of collective magnetic excitations (magnons) in CrI3. Our results establish vertical tunneling as a versatile probe of magnetism in atomically thin insulators.

cond-mat.mes-hall↗

arXiv2017

Extremely large magnetoresistance and Kohler's rule in PdSn4: a complete study of thermodynamic, transport and band structure properties

The recently discovered material PtSn$_4$ is known to exhibit extremely large magnetoresistance (XMR) that also manifests Dirac arc nodes on the surface. PdSn$_4$ is isostructure to PtSn$_4$ with same electron count. We report on the physical properties of high quality single crystals of PdSn$_4$ including specific heat, temperature and magnetic field dependent resistivity and magnetization, and electronic band structure properties obtained from angle resolved photoemission spectroscopy (ARPES). We observe that PdSn$_4$ has physical properties that are qualitatively similar to those of PtSn$_4$, but find also pronounced differences. Importantly, the Dirac arc node surface state of PtSn$_4$ is gapped out for PdSn$_4$. By comparing these similar compounds, we address the origin of the extremely large magnetoresistance in PdSn$_4$ and PtSn$_4$; based on detailed analysis of the magnetoresistivity, $ρ(H,T)$, we conclude that neither carrier compensation nor the Dirac arc node surface state are primary reason for the extremely large magnetoresistance. On the other hand, we find that surprisingly Kohler's rule scaling of the mangnetoresistance, which describes a self-similarity of the field induced orbital electronic motion across different length scales and is derived for a simple electronic response of metals to applied in a magnetic field is obeyed over the full range of temperatures and field strengths that we explore.

cond-mat.str-el↗

arXiv2017

Growth and characterization of BaZnGa

We report the growth, structure and characterization of BaZnGa, identifying it as the sole known ternary compound in the Ba-Zn-Ga system. Single crystals of BaZnGa can be grown out of excess Ba-Zn and adopt a tI36 structure type. There are three unique Ba sites and three M\,=\,Zn/Ga sites. Using DFT calculations we can argue that whereas one of these three M sites is probably solely occupied by Ga, the other two M sites, most likely, have mixed Zn/Ga occupancy. Temperature dependent resistivity and magnetization measurements suggest that BaZnGa is a poor metal with no electronic or magnetic phase transitions between 2\,K and 300\,K.

cond-mat.mtrl-sci↗

arXiv2016

Isotope Effect on Electron-Phonon Interaction in Multiband Superconductor MgB2

We investigate the effect of isotope substitution on the electron-phonon interaction in the multi-band superconductor MgB2 using tunable laser based Angle Resolved Photoemission Spectroscopy. The kink structure around 70 meV in the $σ$ band, which is caused by electron coupling to the E2g phonon mode, is shifted to higher binding energy by ~3.5 meV in Mg(10)B2 and the shift is not affected by superconducting transition. These results serve as the benchmark for investigations of isotope effects in known, unconventional superconductors and newly discovered superconductors where the origin of pairing is unknown.

cond-mat.supr-con↗