Investigation of magnetization dynamics in trilayer width-modulated nanowires

We have investigated the magnetization reversal processes and dynamic behavior of trilayered Py(50 nm)/Pd(tPd)/Py(20 nm) nanowires with periodic width modulation as a function of spacer layer thickness tPd in the range from 0 to 10 nm and compared them with single-layer nanowires. The ferromagnetic resonance spectra show more than three modes that result from a non-uniform demagnetizing field in width-modulated nanowires. We observe that the spacer layer thickness influenced the ferromagnetic resonance spectra, which showed different numbers and values of modes and frequencies due to the different magnetization configurations for different spacer layer thicknesses. We also found that the two ferromagnetic layers are exchange-coupled for tPd = 2 nm nanowire arrays, showing the sharp switching of magnetization from the static measurements and sharp frequency jump from 13.6 to 14.7 GHz around −18 mT from the dynamic measurements. However, for tPd = 10 nm, the two layers switch at different fields, indicating a gradual decrease in magnetization as the reversal is mediated through dipolar coupling. The origin of modes is well explained from the spatial mode profiles of top and bottom magnetic layers. The dynamic responses in this spin-valve-type structure are useful for designing microwave-based spintronic devices

Magnetization dynamics in single and trilayer nanowires.

We have studied the magnetization dynamics of single Py( ) ( = 20 nm, 50 nm) and trilayer [Py(50)/Pd( )/Py(20)] nanowire arrays fabricated over large areas using deep ultraviolet lithography technique. The dynamic properties are sensitive to the field orientation and magnetic film thicknesses. A single resonant mode corresponding to the excitations at the bulk part of the wire is detected in all the single-layer nanowire arrays. Furthermore, the spacer layer thickness influenced the dynamic properties in trilayer samples due to the different coupling mechanisms. A single resonant mode is observed in = 2 nm trilayer nanowires with a sharp frequency jump from 13 GHz to 15 GHz across the reversal regime. This indicates the exchange coupling and the coherence in magnetization precession in the ferromagnetic layers. On the other hand, wires with 10 nm-spacer display two well-resolved modes separated by ∼3 GHz with a gradual change in frequency across the reversal regime from-26mT to-46mT, indicating the presence of long-range dipolar interactions instead of exchange coupling. The spacer layer of the proposed spin-valve-type structure can be tailored for desired microwave splitters or combiners. [Abstract copyright: © 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.

Reconfigurable Logic Operations via Gate Controlled Skyrmion Motion in a Nanomagnetic Device

Owing to the topological protection and the ease of efficient manipulation, skyrmions have emerged as potential candidates for carrying information in future memory and logic devices. Here, we have proposed a reconfigurable skyrmion based two-input logic device architecture. Using micromagnetic simulations, we have demonstrated that the device is capable of performing both OR and AND logic gate functionalities in a reconfigurable manner. Different logic functionality of the device is selected by using a current through a nonmagnetic metallic gate, and the resultant Oersted field controls the trajectory of the skyrmion, which in turn determines the logic states. The logic functions are implemented on a ferromagnet/heavy metal bilayer device structure by virtue of several physical effects, such as the spin-orbit torque, skyrmion-edge repulsion, skyrmion-skyrmion topological repulsion, and skyrmion Hall effect. The skyrmion trajectory has been characterized by estimating the skyrmion Hall angle. A wide range of operations by varying the current density, skyrmion velocity, Dzyaloshinskii-Moriya interaction, magnetic anisotropy, and geometrical parameters have been presented in detail. We believe that our spin orbit torque driven logic design will have potential implications for a high-speed and low-power skyrmion based computing architecture. © 2022 American Chemical Society

Skyrmion Dynamics in Concentric and Eccentric Nano-Ring Structures

Skyrmions are found to be promising for next-generation energy-efficient spintronic applications. Moreover, ultrafast skyrmion dynamics in the gigahertz-band offer an excellent opportunity to exploit such topologically protected nanostructures in high-frequency applications. Here, we present a systematic investigation of the microwave properties of the skyrmions in concentric and eccentric ring structures using micromagnetic simulations. Two gyrotropic modes with clockwise and counterclockwise gyration are observed in skyrmion when excited by an in-plane microwave field. The high-frequency response is found to be enhanced by 3.5 GHz by using a small bias field of 40 mT. The skyrmion dynamics are found to be extremely sensitive to the edge repulsions and a remarkably large frequency shift of 2 GHz of the skyrmion resonance modes is observed by simply varying the position of a skyrmion in an eccentric ring structure. The results are substantiated by directly correlating the observations with inertial mass associated with a skyrmion calculated analytically. The results provide additional functionality of the skyrmions based on their tunable microwave properties which may have potential implications in the field of miniaturized reconfigurable microwave devices. © 1965-2012 IEEE

Magnetization dynamics of single and trilayer permalloy nanodots

We have investigated the magnetization dynamics in single and trilayer circular permalloy nanodots with a diameter of 120 nm using broadband ferromagnetic resonance spectroscopy. For single-layer nanodots, two well-separated modes near the saturation field, a high-frequency center mode due to excitations at the center of the nanodots and a low-frequency edge mode due to the inhomogeneous effective field near the edges, were observed. Both the center mode and the edge mode are found to be sensitive to the thickness of the nanodots. However, for trilayer nanodots, two center modes arise due to the in-phase and out-of-phase precession of spins in magneto-dynamically coupled layers. Our experimental results are substantiated by micromagnetic simulations, which are in good agreement

Investigation of Magnetization Dynamics in Trilayer Width-modulated Nanowires

1.Simulated hysteresis loops of trilayer WMNWs. 2.Experimental hysteresis loops of single-layer width-modulated nanowires (WMNWs). 3.Experimental and simulated FMR spectra of single layer Py(20) and Py(50) WMNWs. 4.Experimental FMR spectra as a function of magnetic field and thickness of spacer layer in trilayer WMNWs. 5.Resonance frequency versus magnetic field plot for single layer WMNWs. 6.FMR spectra as a function of spacer layer thickness and field orientation in trilayer sample