Anjan Barman

Diamond-shaped nanomagnets host closely spaced anisotropic spin-wave modes that selectively interact with lattice-controlled magnetoelastic modes, enabling resonant energy transfer and reconfiguration into a single precessional mode.

Peptide-functionalized gold nanoparticles (AuNPs) provide a model for decoding how the surface-bound secondary structure regulates nano–bio interactions.

Topological insulators host symmetry protected surface states whose functionality is strongly influenced by lattice dynamics and symmetry perturbations. Here, we demonstrate dopant-driven symmetry and phonon engineering in FeSe-doped Bi 2 Te 3 thin films by correlating structural evolution with Raman and terahertz (THz) measurements. At low FeSe concentrations (3%–7%), compressive strain and lattice contraction preserve global centrosymmetry while inducing local inversion symmetry breaking, activating the normally infrared A 1 u 2 phonon in Raman spectra. With increasing doping beyond 7%, the lattice undergoes a compressive to tensile strain crossover accompanied by lattice expansion and microstructural disorder, leading to phonon softening, linewidth broadening, and suppression of the A 1 u 2 mode. At 15% FeSe-doping, a distinct low frequency THz active mode near 36 cm − 1 emerges, indicating the formation of dipole active lattice excitations associated with spatially heterogeneous strain and local polar distortions. Hall measurements reveal a concurrent reduction in carrier mobility and concentration, linking lattice disorder and dopant induced phonon dynamics to suppressed charge transport. These results establish FeSe doping as an effective route to control lattice symmetry, low-energy phonons, and electronic transport in Bi 2 Te 3 , providing a versatile platform for phonon and symmetry engineered topological and spintronic devices.

Three-dimensional artificial spin ice (3D-ASI) is a programmable nanoscale magnetic network showing emergent magnetic charge states with potential for reconfigurable dynamics. Here, we show that magnetic charge states in a 3D-ASI leave experimentally measurable charge-sensitive spectral signatures in the spin-wave spectrum, enabling charge-state readout via magnonics. Using Brillouin light scattering spectroscopy supported by micromagnetic simulations, we demonstrate that charged and charge-neutral vertices produce qualitatively distinct spin-wave spectra in a purely three-dimensional lattice. Spatially resolved mode analysis reveals that magnetic charges selectively control spin-wave localization and quantization, establishing a direct link between vertex microstate and dynamic response. We further demonstrate that configurational anisotropy inherent to the 3D architecture allows spin-wave reconfiguration by varying the orientation of an applied field. These results position spin-wave spectroscopy as a dynamic, noninvasive probe of magnetic charge states and open pathways to reprogrammable, low-power 3D magnonic and neuromorphic devices.

1. Interconnected nanowires, owing to their distinctive three-dimensional (3D) architectures and multifunctional properties, have emerged as a highly significant system for a wide spectrum of advan...

We explore mutually interacting spin waves and acoustic wave modes in addition to a few non-interactive modes through all optical excitation in ordered arrays of Ni ₈₀ Fe ₂₀ nanomagnets.

Control of collective spin excitations by static or dynamic strain is an emerging phenomenon that requires in-depth understanding for design of future spin-wave-regulated devices. Here, we explore mutually interacting spin waves and acoustic wave modes in addition to few non-interactive modes through all optical excitation in ordered arrays of Ni80Fe20 nanomagnets. The acoustic wave originated from elastic deformation resonantly couple to the spin wave via magnetoelastic effect at their overlapping frequency. We demonstrate that the choice of the lattice type in which the magnetic nanodots are arranged is crucial for the observation of the magnetoelastic interaction. Therefore, the study shows that the simultaneous existence of elastic wave and spin wave offer ingeneously advantageous features to pave the way of energy-efficient magnetoacoustic devices.

Heterostructures combining graphene with 3d transition metal ferromagnets (FMs) enable various spin-based phenomena at ultrafast timescales. However, challenges such as the interfacial impedance mismatch, FM deposition-induced defect generation, and interface modification by interfacial coupling or hybridization can impede their functionalization for spin-orbitronics. In this work, we utilize insulating TiOx barrier layers (BLs) to modify the interfacial spin conductance structurally, disentangle spin pumping and magnetic proximity effects (MPE), and establish external control over ultrafast magnetization dynamics in single-layer graphene/TiOx/Co systems. All-optical time-resolved magneto-optical Kerr effect measurements of femtosecond to nanosecond spin dynamics reveal systematic tunability of ultrafast magnetic parameters via barrier engineering. The thickness-dependent damping modulation in Co indicates strong spin pumping, with interfacial spin transparency close to half its physical limit in the presence of an ultrathin BL, where MPE is eliminated. Our results show that appropriately chosen ultrathin BLs can prevent interfacial alterations from ferromagnetic metals, facilitating efficient spin detection in graphene and enhancing control over spin angular momentum dissipation in graphene/FM interfaces.

Spin‐orbit torque (SOT) has many applications in magnetism. Here, a new application is reported – the tunable amplification and spectral filtering of selected spin‐wave (SW) modes in a 2D periodic array of nanomagnets (a “magnonic crystal”) using alternating current SOT (ac‐SOT). Ultrashort laser pulses are used to excite the natural or intrinsic SW modes of the magnonic crystal which is placed in contact with a heavy metal nanostrip into which an alternating charge current is injected to produce an alternating spin current (ASC) in the nanomagnets via the spin Hall effect. The charge current frequency is tuned to the frequency of a specific intrinsic SW mode of the magnonic crystal to amplify the latter by resonant transfer of energy from the ASC to the SW. The amplification can be varied by varying the ac charge current amplitude, resulting in more than ten‐fold increment in the amplitude of some mode(s). Simultaneously, the linewidth of the spectrum for the amplified mode is narrowed. All these features can be explained by coupled mode theory. They improve the signal‐to‐noise ratio, and benefit GHz‐frequency information transmission and analog signal processing with SWs.