arXiv subjects

Tamali Mukherjee

Publications and source records attributed to Tamali Mukherjee.

4 recordsLinked to original sources

arXiv2026

Emergence of Lissajous trajectories in skyrmion oscillator

Understanding the dynamics of current-driven skyrmion is essential for their practical applications. In this study, we apply an ac pulse (a) in x-- direction, and (b) in both x-- and y-- directions through the free layer of a Co/Pt thin film and investigate the motion of the skyrmion. We show that the skyrmion follows the sinusoidal current pulse and behaves like an oscillator in the range of current amplitude 1 $\times$ 10$^{11}$ A/m$^2$ to 1 $\times$ 10$^{12}$ A/m$^2$ and frequency 5 $\times$ 10$^{8}$ rad/s to 1 $\times$ 10$^{10}$ rad/s. For current pulse of (A$_1$sin$\omega_1$t, A$_2$sin($\omega_2$t+$\phi$), 0), the skyrmion forms Lissajous figures in the x-y plane, same as observed in classical mechanics. The results are compared at T = 0 K and T $>$ 0 K to analyze the effect of temperature. As the skyrmion Hall angle ($\theta_{SkH}$) and stochastic thermal fluctuation ($\bm{F}^{Th}$) are functions of temperature, the skyrmion starts deviating from its path at T = 0 K with increasing temperature and eventually generates somewhat deformed Lissajous figures from ideal.

cond-mat.mtrl-sci↗

arXiv2025

Skyrmion manipulation and logic gate functionality in transition metal multilayers

Magnetic skyrmions, due to their topological stability and high mobility, are strong candidates for information carriers in spintronic devices. To advance their practical applications, a detailed understanding of their nucleation and current-driven dynamics is essential. We investigate the formation and manipulation of skyrmions in a square nano structure (200 $\times$ 200 nm$^{2}$, 1 nm thick) of PdFe/Ir(111) multilayers subjected to nano second current pulses with magnitude ranging from (1-5)$\times$10$^{11}$ A/m$^2$. Using micromagnetic simulations, we demonstrate controlled motion of skyrmion under different types of spin-transfer torque (STT). The calculated skyrmion Hall angle (SkH) for Slonczewski type STT is ${θ_{SkH}^{SL}} = 89.53^{\circ}$ for PdFe/Ir(111) multilayers which ensures the edge accululation of skyrmion like a track within the nano structure and we extend this idea further for different shape engineering of skyrmion in 4d tranisition metal multilayers by manipulating the magnitude and direction of current pulses. Next, we investigate the influence of voltage-controlled magnetic anisotropy ranging from (1.4 - 4.2) $\times$ 10$^6$ J/m$^3$ with external magnetic field B$_{ext}$ = 2 T, and (0 - 2.8) $\times$ 10$^6$ J/m$^3$ with B$_{ext}$ = 3 T respectively, on skyrmion dynamics for designing anisotropy-engineered barriers to guide their trajectories in PdFe/Ir(111) multilayers. We use further these barriers to implement basic logic operations, including OR and AND gates, with skyrmions representing binary states. The calculatd skyrmion Hall angle for Zhang-Li type STT in PdFe/Ir(111) multilayers is ${θ_{SkH}^{ZL}} = 3.26^{\circ}$. Consequently, the skyrmions propagate predominantly along the direction of the applied current with minimal deflection, a feature that renders them highly suitable for logic operations.

cond-mat.mtrl-sci↗

arXiv2025

Role of magnetic anisotropy constant orders and thermal noise on skyrmion formation in the Co/Pt square nanostructure

Skyrmions, which are topologically stable magnetic structures, have manifested promising features to be used as an information carrier in new-age, non-volatile data storage devices. In this article, Co/Pt square nano-structure with Co-free layer thickness in the range of 1 nm to 5 nm is taken to study the controlled creation of skyrmions. The magnetization dynamics controlled by the current-induced spin transfer torque help to nucleate skyrmions by transforming the perpendicularly magnetized ground state. This process leads to a stable state of isolated skyrmions via a complex transformation of the Neel wall following its image inversion. Skyrmion numbers vary with increasing thickness as the current density gradually increases. The impact of higher-order anisotropy constants (up to the second order) on the relaxed state of a system, compared to first-order anisotropy alone, has been examined. Additionally, the effect of temperature on the formation of skyrmions has been analyzed for all thicknesses.

cond-mat.mtrl-sci↗

arXiv2024

Interplay between interfacial Dzyaloshinskii Moriya interaction and magnetic anisotropy in 4d transition metal multilayers for skyrmion nucleation

Skyrmions refer to small swirling spin structures that emerge in ferromagnetic materials and show promising features to be used as a `bit' of information in future spintronic devices. Our research explores the possibility of nucleating skyrmions in X-Fe/Ir(111) multilayer nano-structure where, X is one of the 4d transition metals, such as, Pd, Rh, Ru, Mo and Nb. The resulting final state is determined by the competition between the frustrated exchange interaction, primarily contributed by the top 4d transition metal layer, and the Dzyaloshinskii-Moriya interactions induced significantly by the 5d heavy metal Ir(111) layer. We apply a perpendicular dc magnetic field to the nano-structure and observe gradual phase transformation from the spin spiral ground state to a stable relaxed state of nano-scale skyrmions . A proper choice of magnetic anisotropy and interfacial Dzyaloshinskii-Moriya interaction leads to a range of external magnetic fields essential for the existence and stability of skyrmions. By raising the temperature, we assess the thermal stability of the nucleated skyrmions to evaluate their potential as information carriers in future spintronic devices.

cond-mat.mtrl-sci↗