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Special Seminar | X-Ray Science Division

Dynamic magnetic properties and spin waves in magnetic nanostructures

XSD/MM Special Presentation

Abstract: Progress in magnetic recording media, lead to the development of patterned recording media. Growing demand for higher lateral density in magnetic recording and for higher speed of memory operation focused the attention of many researchers on the spin dynamics in the patterned nano-meteric magnetic elements with controlled geometry [1,2,3]. Spin waves are perturbations of magnetic ordering in materials, it is very important to understand the processes of excitation, propagation and interaction of spin waves in nano magnetic elements, with a view to new technologies that will complement the modern applications of electronics and spintronics.

In the present study, we investigate the dynamics magnetic properties and the spin waves modes in the continuous films and array of nanometer-sized objects of Permalloy (Ni81Fe19), using the broadband ferromagnetic resonance measurements (VNA-FMR) and micromagnetic simulations. Arrays of magnetic nanostructures with thickness of 50 nm were produced by e-beam lithography and then followed by magnetron sputtering and lift-off and plasma etching processes. We observed the vortex state and several other low-frequency spin wave modes for elliptical magnetic nanostructures. The simulated absorption spectra reproduce the main features of the experimental results.

A detailed analysis of the resonant modes at zero field shows that, the resonance frequency of the observed spin wave modes is increasing as we reduce the size of these elliptical nanostructures. The samples present a great diversity of results with increasing complexity. The relation of the spin waves with the symmetries of the nano- objects and the distribution of the free magnetic energy inside them is analyzed with a special interest. Additionally, the boundary between the magneto-static waves governed by the dipole interaction and the spin waves, where the exchange interaction is dominant are explored. The results of the following study, could pave a path for applications in the magnonic devices.