Showing papers by "Andrzej Maziewski published in 2019"

Fundamental Limits on the Repetition Rate of Photomagnetic Recording

Abstract: In the last decade it was demonstrated that the fastest way to write information employs ultrashort laser pulses. Naturally such experiments raise questions about the ultimate limit of repetition rate at which light can switch a medium between stable bit states. Here the authors demonstrate that with femtosecond pulses it is possible to write and rewrite magnetic bits in iron garnet with a frequency of up to 20 GHz, with the maximum repetition rate being defined by the frequency of ferromagnetic resonance in the field of photoinduced magnetic anisotropy. This finding reveals the principles to be employed in achieving magnetic recording at frequencies far beyond today's state of the art.

Mapping magnetization states in ultrathin films with Dzyaloshinskii–Moriya interaction

Abstract: To succeed in the next generation of magnetic storages, nanomagnetic structures must be engineered to allow modulation of magnetization amplitude and spatial period. We demonstrate computationally how magnetic nanostructures states (domains with narrow wall, skyrmions, spin spirals, conical spin-spiral, and in-plane magnetization configuration) can be designed in ultrathin films with a Dzyaloshinskii-Moriya interaction (DMI) by adjusting two material parameters: perpendicular magnetic anisotropy characterized by the quality factor Q, and reduced DMI constant Δ. For a broad range of Q and Δ parameters, the magnetization states are mapped in (Q, Δ) diagrams and characterized by the periodicity (p) of spatial distribution of magnetization and the mean value of the square of an out-of-plane normalized magnetization component 〈malt;subagt;zalt;/subagt;alt;supagt;2alt;/supagt;〉. We explain the transitions between different magnetization states and describe phase transition curves in terms of vanishing of the domain wall energy for both 0≤Qalt;1 and Qagt;1 cases. We show that by changing Δ and/or Q and approaching the phase transition curves, the discontinuous transitions accompanied by jumps of both period and amplitude take place.

On defects' role in enhanced perpendicular magnetic anisotropy in Pt/Co/Pt, induced by ion irradiation.

Abstract: Modifications of magnetic and magneto-optical properties of Pt/Co(d Co )/Pt upon Ar+ irradiation (with energy 1.2, 5 and 30 keV) and fluence, F at the range from 2 · 1013-2 · 1016 Ar+ cm-2) were studied. Two 'branches' of increased perpendicular magnetic anisotropy (PMA) and enhanced magneto-optical response are found on 2D (d Co , F) diagrams. The difference in F between 'branches' is driven by ion energy. Structural features correlated with magnetic properties have been analysed thoroughly by x-ray diffraction, Rutherford backscattering spectrometry and positron annihilation spectroscopy. Experimental results are in agreement with TRIDYN numerical calculations of irradiation-induced layers intermixing. Our work discusses particularly structural factors related to crystal lattice defects and strain, created and modified by irradiation, co-responsible for the increase in the PMA.