arXiv subjects

Adam Krysztofik

Publications and source records attributed to Adam Krysztofik.

4 recordsLinked to original sources

arXiv2026

Coherent control of thermal transport with pillar-based phononic crystals

Two-dimensional phononic crystals (PnCs) formed by a periodic array of holes in a suspended membrane have previously been used to coherently control thermal conductance at low temperatures by modifying the phonon dispersion, thereby altering the phonon group velocities and the density of states. Here, in contrast, we demonstrate that PnCs formed by a periodic array of Al pillars on an uncut \SiN membrane can also be used to achieve similar coherent control. We have measured and simulated the thermal conductance of four pillar-based PnCs with different lattice constants ranging from 0.3 to 5 $\mu$m at sub-Kelvin temperatures, showing a strong up to an order of magnitude reduction in thermal conductance compared to an unaltered membrane. For the larger lattice constants $> 1 $ $\mu$m, however, the experiments do not agree with the coherent theory simulations, which we interpret as a breakdown of coherence induced by increasingly effective diffusive scattering due to the roughness of the Al pillar surfaces.

cond-mat.mes-hall↗

arXiv2019

Ultra-low damping in lift-off structured yttrium iron garnet thin films

We show that using maskless photolithography and the lift-off technique, patterned yttrium iron garnet thin films possessing ultra-low Gilbert damping can be accomplished. The films of 70 nm thickness were grown on (001)-oriented gadolinium gallium garnet by means of pulsed laser deposition, and they exhibit high crystalline quality, low surface roughness, and the effective magnetization of 127 emu/cm3. The Gilbert damping parameter is as low as 5x10-4. The obtained structures have well-defined sharp edges which along with good structural and magnetic film properties pave a path in the fabrication of high-quality magnonic circuits and oxide-based spintronic devices.

cond-mat.mtrl-sci↗

arXiv2019

Characterization of spin wave propagation in (111) YIG thin films with large anisotropy

We report on long-range spin wave (SW) propagation in nanometer-thick yttrium iron garnet (YIG) film with an ultralow Gilbert damping. The knowledge of a wavenumber value $|\vec{k}|$ is essential for designing SW devices. Although determining the wavenumber $|\vec{k}|$ in experiments like Brillouin light scattering spectroscopy is straightforward, quantifying the wavenumber in all-electrical experiments has not been widely commented upon so far. We analyze magnetostatic spin wave (SW) propagation in YIG films in order to determine the SW wavenumber $|\vec{k}|$ excited by the coplanar waveguide. We show that it is crucial to consider the influence of magnetic anisotropy fields present in YIG thin films for precise determination of SW wavenumber. With the proposed methods we find that experimentally derived values of $|\vec{k}|$ are in perfect agreement with that obtained from electromagnetic simulation only if anisotropy fields are included.

cond-mat.mes-hall↗

arXiv2018

Experimental Evidence of Non-Negligible Imaginary Part of Spin Mixing Conductance and Its Impact on Magnetization Dynamics in Heavy-Metal|Ferromagnet Bilayers

The paper concerns experimental verification of the magnitude of imaginary part of spin mixing conductance in bilayers comprising heavy metals. We present results of broadband ferromagnetic resonance studies on heterostructures consisting of Finemet thin films covered by Pt and Ta wedge layers with the aim to observe spin pumping effects and to evaluate both the real and imaginary parts of the spin mixing conductance. The experimental results are analyzed in the framework of a recent microscopic theory which allows us to estimate the value of the interfacial spin-orbit interaction and confirm its important role. In particular, we show that the imaginary part of spin mixing conductance cannot be regarded as negligible and we discuss its influence on magnetization dynamics. For Finemet|Ta bilayers, the ratio $\mathrm{Re}[g_{eff}^{\uparrow\downarrow}]/\mathrm{Im}[g_{eff}^{\uparrow\downarrow}]=$ 0.38, that is, the field-like torque dominates over the damping-like torque in such system. Consequently, relatively small enhancement of precession damping with respect to significant total torque exerted on the magnetization in Finemet|Ta system offers an attractive perspective for an application in the next-generation magnetic random-access memory cells.

cond-mat.mes-hall↗