@misc{Gruszecki2023,
title = {Novel environment for spin wave propagation: from periodic magnetization textures towards space-time magnonic crystals},
author = {Paweł Gruszecki},
url = {https://zfn.web.amu.edu.pl/sonata-15/},
year = {2023},
date = {2023-12-01},
abstract = {A unique property of spin waves (SWs) is the fact that they propagate in magnetic media. Features of an environment for SWs can be easily molded, e.g., by the external factors like the magnetic field, but also by the internal magnetization texture. One of the efficient ways to modulate the effective media properties is the introduction of periodical modulation of them in the space. In the case of SWs, such media are called magnonic crystals (MCs). The concept of periodic modulation was just recently extended from space into space-time, leading to the idea of a time crystal by Wilczek in 2012. The definition of a time crystalline structure is deduced from ordinary space crystals where the critical criterion for the formation of a time-crystal is the breaking of the time translation symmetry (like spatial translation symmetry break is essential for ordinary space crystals). The combination of space and time symmetry breakings defines a so-called Space-Time Crystal (STC) that exhibits periodicity in space and time. In the frame of this Project, we unite the fundamental STC concept within the quantum regime with the world of magnonics introducing space-time MCs (STMCs) and present an exceptional case of nonlinear wave physics in a comparatively large structure. The general objective of this Project is the analysis of SW dynamics in magnetization textures that are, firstly, periodical in space, and, ultimately, in a new class of magnetization textures that are periodical both in space and time. The main research hypothesis is based on the assumption regarding a unique potential of nonuniform magnetization textures, especially those exhibiting space-time periodicity, as a medium for SW propagation.

We will study the properties of SW propagation along domain walls of different internal structures, starting from a single domain wall and, then, focusing on various periodical magnetization textures that can be either uniform or non-uniform across the thickness, i.e., we will study magnetization textures from periodic aligned stripe domains separated by narrow domain walls to spiral domain patterns requiring antisymmetric exchange interaction, so-called Dzyaloshinskii–Moriya interaction (DMI) to be stabilized. In these studies, the main Focus will be paid on the systems with perpendicular magnetocrystalline anisotropy (PMA) and DMI. Multifunctionality of single and multiple domain walls, as nanochannels with nonreciprocal properties supporting twisted SW beams and as a source of SWs, is expected to be achieved. The tenability of the SW spectrum and propagation characteristics of a periodical in one space dimension magnetization textures will be studied. The special attention, however, will be paid to a new class of magnetization textures that are both periodic in time and space. Various scenarios of condensation of these systems and their influence on SW dynamics will be extensively studied.

In this Project, we will address a few important issues in magnonics and in physics, in general. Firstly, we will study SW channeling in ultra-narrow single-mode waveguides created by domain walls of various internal structures focusing on their nonreciprocal properties and existence of SW modes behaving as twisted beams, i.e., beams with a definite and controllable orbital angular momentum. Secondly, we will employ domain walls to excite sub 100 nm wavelength SWs, which is another big challenge in magnonics nowadays. Thirdly, we will analyze how the magnetic properties of the media influence both magnetization statics and dynamics. Finally, we will use the acquired knowledge to analyze the condensation of a periodical in both space and time magnetization textures, and then their features for SW propagation. We will verify whether the STMCs form band structures at room temperature and if magnons interact with the lattice of STMCs like in regular crystals. The results of this Project will provide progress concerning state-of-the-art and ensure a significant contribution to the development of magnonics. Additionally, we hope, that our research can promise outstanding new opportunities in fundamental research in nonlinear wave physics.

The research bases on micromagnetic simulations supported by semi-analytical analysis of SW dynamics combined with atomistic simulations. Although the Project mainly bases on the theoretical and numerical investigation, the research will also be conducted in collaboration with experimental groups whenever possible.},
howpublished = {2020},
note = {NCN Sonata 15, No. 2019/35/D/ST3/03729, budget: 938 928,00 PLN},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}