@misc{klosopuslap,
title = {Low-loss current- and flux quanta-controlled magnonics},
author = {Jarosław W. Kłos},
url = {https://isik.amu.edu.pl/flumag/},
year = {2026},
date = {2026-01-01},
abstract = {Ferromagnetism (F) and superconductivity (S) belong to the most fundamental phenomena in condensed matter physics. Due to incompatible spin orders and antagonistic responses to an external magnetic field, their combination gives rise to numerous novel phenomena. However, the coexistence of F and S in bulk systems remains a rare circumstance peculiar to complex compounds. At the same time, the coexistence of S and F can be readily achieved in artificial ferromagnet/superconductor (F/S) heterostructures. In this regard, F/S hybrid structures can be classified either as proximity-coupled (i.e., electrically connected) or as stray-field-coupled (i.e., electrically insulated).

The project FulMag is formulated to scrutinize the physics of spin waves in electrically insulated F/S heterostructures where the interplay of spin-wave dynamics in a ferromagnet with stray fields produced by eddy currents in a superconductor can be used to explore novel magnonic functionalities in the emerging domain of cryogenic magnonics.

We will conceive theoretical foundations of the spin-wave dynamics in F/S hybrid structures and elaborate novel concepts for the excitation, manipulation, and detection of spin waves, which are beyond the reach of traditional magnonic approaches. The focus will be pointed towards cryogenic magnonic nano-devices operating preferably in the short-wavelength (exchange) spin-wave regime. Their realization will be underpinned by the fundamental physical phenomena of Meissner screening and the Cherenkov radiation of magnons originating from moving magnetic flux quanta (Abrikosov vortices). A complete and multidisciplinary theoretical description, encompassing finite-element micromagnetic simulations in conjunction with the state-of-the-art phenomenological models relying upon the Landau-Lifschitz-Gilbert equation for dipole-exchange spin-waves and the London equations or Ginzburg-Landau model of superconductivity, will allow us to design F/S hybrids with targeted functionalities. We are going to use the stray field generated by the superconducting pattern to confine and guide the spin waves in a homogeneous ferromagnetic layer. We are planning to investigate spin-wave couplers realizing the non-reciprocal spin-wave transmission/reflection and graded-index structures controlling the spin-wave refraction. Device prototypes will be examined at microwave frequencies up to 70 GHz, vector magnetic fields up to 9 T, temperatures down to 10 mK, and by time- and spatially-resolved optical spectroscopy methods. The project results will have a great impact on the domains of microwave magnetism, superconductivity, and emerging magnon-based quantum technologies.},
howpublished = {2023},
note = {NCN OPUS-LAP, No. 2021/43/I/ST3/00550, budget: 1 042 994 PLN},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}

@misc{klospreludium,
title = { Spin waves in hybrid nanostructures – the role of surface anisotropy},
author = {Jarosław W. Kłos},
url = {https://isik.amu.edu.pl/spin-waves-hybrid-nanostructures-and-anisotropy/},
year = {2025},
date = {2025-09-30},
abstract = {The magnonic systems (nanostructures supporting the spin wave dynamics) can be combined by magnetoelastic interaction with phononic systems (processing the elastic waves) or by the electromagnetic coupling with superconducting structures (where the superconducting eddy currents generate magnetic stray field). In these hybrid structures, the impact of the surface anisotropy seems to be very important for the boundary condition of combined excitations: (i) magnetoelastic waves or (ii) spin waves coupled to eddy currents. Moreover, the spin waves pinning resulting from the surface anisotropy will affect the spatial crosssection of elastic waves and spin waves (for magnonic-phononic hybrids) or dynamic magnetic fields produced by spin wakes and eddy currents (for magnonic-superconducting hybrids).

The main scientific goal of the project is to investigate the impact of surface anisotropy on the interaction between spin waves and elastic waves (or eddy currents) in hybrid magnonic-phononic (and magnonicsuperconducting) structures. The research hypothesis is that the surface anisotropy can change the conditions at the interface between magnonic and non-magnonic components of hybrid system boundary for dynamic excitation. We think this opened the possibility to tailor the coupling between spin waves and non-magnetic excitations by changing the state of the interface between the subsystems in a hybrid structure.},
howpublished = {2021},
note = {NCN PRELUDIUM-BIS-2, No. 2020/39/O/ST5/02110, budget: 484 129 PLN},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}

@misc{Kłos2021,
title = {Modification of the interactions between magnons and phonons in periodic nanostructures by adjusting the structural and material parameters},
author = {Jarosław W. Kłos},
url = {http://isik.amu.edu.pl/interactions-between-magnons-and-phonons/},
year = {2021},
date = {2021-12-01},
abstract = {The project is focused on the interactions between magnons and phonons in nanostructures. We are going to consider the system in which the existence both spin waves and elastic waves is possible. The main goal of this Project is modification of the interaction between magnons and phonons by adjusting the structural and material parameters of periodic nanostructures. The investigated periodic structures will be designed to alter (to enhance or to weaken) the dynamical magneto-elastic interactions by deliberate introduction of structural and material changes or by adjustment of the external magnetic field. We plan to study the systems composed of elastic slab loaded by periodic array of elements deposited on its surface. The elements (stripes or dots) can be deposited directly on the dielectric substrate or on the thin metallic (ferromagnetic) underlayer. The deposited elements can be both magnetic and nonmagnetic. The enhancement is possible when the magnonic and phononic bands coincides in frequency domain and ensured for the surface elastic waves (of Rayleigh and Sezawa type) localized in the area where the ferromagnetic elements (underlayer and stripes or dots) are located (i.e. on the surface). The elastic stress concentrated in ferromagnetic (magnetostrictive) subsystem induces the magneto-elastic coupling which can damp or amplify the spin waves dynamics at selected resonance frequencies (depending if the elastic wave is thermally activated or generated in the form of coherent acoustic wave). Due to the periodicity of phononic (magnonic) subsystem the phononic (magnonic) dispersion will be folded. This allows to fulfill the resonance conditions for strong magneto-elastic coupling at a few frequencies corresponding to the multiple crossing of dispersion bands of phononic and magnonic systems. The magneto-elastic coupling can be also tuned in periodic nanostructures be adjusting the external magnetic field. The appropriately chosen magnetic field can the enhance (or reduce) the overlapping of magonic and phononic bands by shifting of the magnonic spectrum in frequency domain. This leads to the increase (or decrease) of the strength of magneto-elastic interactions. For selected systems in which strong magneto-elastic coupling were observed, we are going to investigate (numerically and experimentally) the possibility of spin wave (elastic wave) amplification by the interaction with elastic wave (spin wave) generated by piezoelectric transducers (micro stripe antenna). The outcomes, we will obtain form this study, will allow us to verify the research hypothesis about the possibility of change of magneto-elastic coupling by periodic patterning of the system.

The research plan encompasses both theoretical and experimental investigations covering the whole cycle of research: numerical simulation – fabrication – characterization – interpretation and theoretical analysis. The theoretical research will be focused on solution of equations describing dynamics of elastic waves (classical theory of elasticity) and spin waves (Landau-Lifshitz equation). The magneto-elastic interactions will be included into Landau-Lifshitz equation be adding the additional term to effective field describing the magnetic fields induced by elastic – determined by the solution of the equations of theory of elasticity. The calculations will be performed with the aid of finite element method, plane wave method and discrete dipole method. The samples will originate from own resources or will be acquired from collaborating groups (third partners) which use the following techniques: electron-beam lithography and focused ion beam epitaxy. The topology of sample will be investigated using: polarization microscopy and atomic force microscopy. The spin wave and elastic wave spectra will be measured with the aid of: Brillouin spectrometer and vector network analyzer.

The magnonics, based on spin wave excitations magnetic material, is a promising branch of technology used for signal processing, and transmission. The one of the main obstacles in the development of this field is damping of spin waves. Nowadays a lots of efforts is concentrated on reduction or on controlling of damping. It is especially important for sophisticated magnonic systems (like magnonic crystals) where the group velocity of spin waves is usually reduced. To achieve long range of spin wave propagation, we have to take spatial care about its life time and amplification of waves in such systems. Our research are focused on these issues. We plan to use elastic waves to amplify spin waves in magnonic nanostructures.},
howpublished = {2016},
note = {NCN OPUS 11, No. 2016/21/B/ST3/00452, budget: 999 980,00 PLN },
keywords = {},
pubstate = {published},
tppubtype = {misc}
}