Splitting of spin-wave modes in thin films with arrays of periodic perturbations: theory and experiment

Abstract

A joint theoretical-experimental study focusing on the description of the ferromagnetic resonance response of thin films in the presence of periodic perturbations introduced on the upper film surface is presented. From the viewpoint of theory, these perturbations may exist in the form of any kind of one-or two-dimensional rectangular defect arrays patterned onto one surface of the magnetic film. Indeed, the defects may be pits or bumps, or ionimplanted regions with a lower saturation magnetization. The complete set of response functions, given by the components of the frequency and wavevector dependent dynamic magnetic susceptibility tensor of the film exposed to microwave excitation, are provided and are used to explain the experimental data. This allows us to obtain the response of the system due to microwave absorption, from which the zero wave-vector spin-wave modes in the fieldfrequency spectra, including their intensity, are calculated. Explicit calculations for periodic defects featuring the shape of stripes, dots and rectangles are given

Magnetic anisotropy, damping, and interfacial spin transport in Pt/LSMO bilayers

“…For Py, the peaks in the linewidth were found to disappear when the film was magnetized parallel to the stripe-like defects. 41,42 The absence of the peaks in our linewidth data for magnetization along the [100] axis in Fig. 4(a) suggests that the Pt/LSMO bilayer films develop stripe-like magnetic defects oriented along this axis.…”

Role of internal demagnetizing field for the dynamics of a surface-modulated magnonic crystal

“…[17][18][19][20][21][22] In previous studies, it was already shown that MCs can be used as grating couplers, 23 for magnonic logic, [24][25][26][27] filter 28 and sensor 29 applications, and moreover, as a tool to access important material properties, such as the exchange constant, at high precision. 30 In order to investigate the effect of the internal demagnetizing field H int d on the spin-wave properties, the dynamics of a surface-modulated magnonic crystal (SMMC) [31][32][33] were reconstructed from 'bottom-up' as sketched in Fig. 1.…”

Spin-wave non-reciprocity in magnetization-graded ferromagnetic films

“…One of the scientific interests is based on promising applications for signal processing devices, since the SW wavelength is shorter than those of electromagnetic waves in the GHz frequency range [2,5], allowing for better prospects for the miniaturization of magnonic devices [6]. This, added to the fact that the magnon bandstructure can be enriched with the artificial modulation of the magnetic media [7][8][9][10][11][12][13][14][15][16][17][18], has stimulated experimental and theoretical advances in the emerging field of magnonics. Recently, it has been theoretically predicted and subsequently proven experimentally, that such waves in FM thin films can couple to a heavy-metal layer with strong spin-orbit coupling, as evidenced by a considerable frequency non-reciprocity due to the interfacial Dzyaloshinskii-Moriya interaction [19][20][21][22][23][24][25][26].…”