Devi Chandrasekhar Kakarla

Low‐dimensional magnets, particularly 2D systems, offer a rich platform for realizing unconventional multiferroic mechanisms, especially when multiple polarization channels coexist. In the quasi‐2D antiferromagnet CrSbS ₃ , which crystallizes in the centrosymmetric orthorhombic space group Pnma and orders magnetically at T _N ≈ 90 K, two independent polarization mechanisms are uncovered. A weak spontaneous polarization (P ₁ ) emerges near T _E ≈ T _N at zero field, driven by partial Cr charge transfer. Synchrotron XRD refinements reveal anomalies in bond valences and average Cr─S bond length, XAS detects subtle modifications in local electronic states, and Raman spectroscopy uncovers anomalous phonon softening, indicating a charge‐transfer‐driven reconstruction of the lattice and phonon. In addition, second‐harmonic generation (SHG) measurements exhibit a clear enhancement below T _E , directly confirming inversion‐symmetry breaking and supporting the emergence of the spontaneous polarization P ₁ . Further, neutron diffraction reveals a C‐type antiferromagnetic structure described by the magnetic space group Pnm'a , which breaks inversion symmetry and induces an additional polarization (P ₂ ) under applied magnetic fields. Critical exponent analysis ( β ≈ 0.23(2)) highlights quasi‐2D magnetism. These results establish CrSbS ₃ as a rare high‐ T _c / T _N (∼90 K) type‐II multiferroic, where charge, spin, lattice, and phonon degrees of freedom cooperatively produce robust ferroic responses in a 2D framework.

The magnetic Weyl semimetal Co 3 Sn 2 S 2 has garnered significant experimental and theoretical interest, particularly regarding its electronic structure and transport properties. In this study, we comprehensively investigated the effects of Fe and Ni substitution in Co 3 Sn 2 S 2 . The temperature-dependent Seebeck coefficient ( S ) implies that the reduction of the band gap and the shift in the Fermi level ( E F ) due to Fe and Ni substitution, which was supported by angle-resolved photoemission spectroscopy results. These band-structure modifications influence not only thermoelectric (TE) performance but also the anomalous Hall conductivity ( σ xy A ). Specifically, Fe substitution increases σ xy A via skew scattering, while Ni substitution increases σ xy A via intrinsic deflection with minor skew scattering. Additionally, the Fe and Ni dopant-induced changes in the c / a ratio were demonstrated using high-resolution powder synchrotron x-ray diffraction, which explains the different modulation in the magnetic anisotropy of Co 3 Sn 2 S 2 due to the magnetostriction effect. Notably, the oxidation states of Co, Fe, and Ni in each single crystal were confirmed as 0 using x-ray absorption near-edge structure analysis, further explaining the dopant-induced suppression in ferromagnetism of Co 3 Sn 2 S 2 . These findings provide deeper insight into the band-filling effects on both TE and anomalous Hall transport in Co 3 Sn 2 S 2 , offering perspectives for topological spintronics and TE applications.

Cluster magnetism has emerged as a fertile platform for exploring unconventional magnetic and dielectric phenomena in complex oxides. In the polar compound Ba${}_{6}$Nd${}_{2}$Fe${}_{4}$O${}_{15}$, a detailed examination of temperature- and field-dependent magnetic, thermal, and dielectric properties reveals a distinct field-induced transition from an antiferromagnetic to a ferrimagnetic phase, accompanied by pronounced magnetodielectric coupling. The study establishes a direct connection between spin tetramer interactions and lattice polarization, demonstrating how localized spin clusters mediate strong cross-correlations between electric and magnetic orders. These results deepen the understanding of cluster-based magnetodielectric phenomena and their microscopic origins in polar magnetic oxides.