Spin Waves in Magnonic Crystals and Hybrid Ferromagnetic Structures

A special issue of Magnetochemistry (ISSN 2312-7481). This special issue belongs to the section "Magnetic Materials".

Deadline for manuscript submissions: 31 December 2024 | Viewed by 2897

Special Issue Editor


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Guest Editor
Department of Physics and Earth Sciences, University of Ferrara, I-44122 Ferrara, Italy
Interests: spin waves; magnonic crystals; artificial spin ice; artificial quasi-crystals; nanomagnetism

Special Issue Information

Dear Colleagues,

In the last decade, the increasingly compelling need for alternatives to the electric current in information technology (IT) has raised interest regarding spin waves (SWs), which do not involve charge transfer and hence are promising ultra-low-dissipation information carriers. Since SWs have nanometric wavelengths in the GHz range (of IT interest), they can be manipulated at the nanoscale in suitably designed nanostructured periodic lattices (Magnonic Crystals) through Bragg diffraction. Their frequency/wavevector dispersions and hence propagation properties can be tailored by the choice of the lattice design and tuned by an external magnetic field. When associated with any ferroelectric layers, in multiferroic systems, such tunability might be enhanced by the possibility of a voltage-control over SW propagation (exploiting the inverse magnetoelastic effect between ferroelectric and ferromagnetic layers). A new source of degrees of freedom for controlling SW propagation consists of stacks of two or more ferromagnetic layers (Vertical Magnonics) with different geometries, from unpatterned films to lattices of different symmetry and element shape (Hybrid Magnonics), and in particular artificial spin ice (ASI) layers and artificial quasi-crystals (AQCs). ASI lattices and AQCs offer a variety of different stable configurations in any given field, based on the vertex frustration offered by the topology of the specific structure. The static and dynamic interplay among such layers, even with very different geometries, is believed to introduce new concepts to the issue of SW propagation.

The aim of this Special Issue is to collect experimental investigations ranging from sample fabrication and characterization issues to any static or dynamic measurements (MOKE loops, FMR spectra, Brillouin light scattering measurements, etc.), and at the same time to present the most relevant theoretical models and micromagnetic simulations performed not only to interpret experiments, but also to predict and unveil any subtle dynamic effects or new regularities emerging out of the complexity itself of the systems. Future applications of SW computing, interferometry, sensing and logic devices are also definitely welcome.

Dr. Federico Montoncello
Guest Editor

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Keywords

  • spin waves
  • magnonic crystals
  • artificial spin ice
  • artificial quasi-crystals
  • nanomagnetism

Published Papers (2 papers)

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Research

11 pages, 4377 KiB  
Article
Nano-Magnonic Crystals by Periodic Modulation of Magnetic Parameters
by Alison Roxburgh and Ezio Iacocca
Magnetochemistry 2024, 10(3), 14; https://doi.org/10.3390/magnetochemistry10030014 - 21 Feb 2024
Viewed by 1174
Abstract
Magnonic crystals are metamaterials whose magnon behavior can be controlled for specific applications. To date, most magnonic crystals have relied on nanopatterning and magnetostatic waves. Here, we analytically and numerically investigate magnonic crystals defined by modulating magnetic parameters at the nanoscale, which predominantly [...] Read more.
Magnonic crystals are metamaterials whose magnon behavior can be controlled for specific applications. To date, most magnonic crystals have relied on nanopatterning and magnetostatic waves. Here, we analytically and numerically investigate magnonic crystals defined by modulating magnetic parameters at the nanoscale, which predominantly act on exchange-dominated, sub-100 nm magnons. We focus on two cases: the variation in the exchange constant, and the DMI constant. We found that the exchange constant modulation gives rise to modest band gaps in the forward volume wave and surface wave configurations. The modulation of the DMI constant was found to have little effect on the magnonic band structure, leading instead to a behavior expected for unpatterned thin films. We believe that our results will be interesting for future experimental investigations of nano-designed magnonic crystals and magnonic devices, where material parameters can be locally controlled, e.g., by thermal nano-lithography. Full article
(This article belongs to the Special Issue Spin Waves in Magnonic Crystals and Hybrid Ferromagnetic Structures)
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19 pages, 13944 KiB  
Article
Dynamic Footprints of the Specific Artificial Spin Ice Microstate on Its Spin Waves
by Pietro Micaletti and Federico Montoncello
Magnetochemistry 2023, 9(6), 158; https://doi.org/10.3390/magnetochemistry9060158 - 16 Jun 2023
Cited by 1 | Viewed by 1318
Abstract
We present a micromagnetic investigation of the spin dynamics at remanence (zero applied field) in a periodic square artificial spin ice (ASI) prepared four different microstates (i.e., with zero, two or four magnetic charges at the vertex). The ASI elements consist of permalloy [...] Read more.
We present a micromagnetic investigation of the spin dynamics at remanence (zero applied field) in a periodic square artificial spin ice (ASI) prepared four different microstates (i.e., with zero, two or four magnetic charges at the vertex). The ASI elements consist of permalloy elliptical dots with a fixed long axis, and a variable width and interdot separation. For each vertex configuration, we compute the equilibrium ground state at zero applied field by relaxing a previously set magnetic configuration (microstate). After the excitation of such ground state, we perform a Fourier analysis obtaining frequency spectra and space phase profiles. We discuss the behavior of the spectra in changing the system’s microstate and geometry, with reference to the spin mode space profiles, magnetization configuration, and effective internal field. Our results draw a correlation between ASI macrospin orientation at vertex and a few important dynamic properties like a phase-shift in the mode profiles or the frequency gap between the edge and fundamental modes. We suggest a few specific experiments to validate of our predictions, as well as applications in the field of interferometric magnonic devices. We believe that our results can help, from the fabrication stage, in tailoring the appropriate ASI geometry for specific application purposes. Full article
(This article belongs to the Special Issue Spin Waves in Magnonic Crystals and Hybrid Ferromagnetic Structures)
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