A theory is developed for dispersion characteristics of spin waves in ferromagnetic films taking into account both dipole-dipole and exchange interactions, crystallographic anisotropy and mixed exchange boundary conditions on the film surfaces. An arbitrary orientation of the external bias magnetic field with respect to the orientation of crystallographic axes and the film normal is assumed. The influence of crystallographic anisotropy on the spin wave spectrum of a ferromagnetic film is discussed. The theoretical results obtained are compared with the results of experiments performed in yttrium-iron garnet (YIG) and Mn-ferrospinel films.
Clear advantages of nanopatterned Pd/Co fi lms over continuous Pd/Co fi lms are demonstrated as candidates for future hydrogen gas sensing devices based upon hydrogen-absorption-modifi ed ferromagnetic resonance. Nanopatterning results in a higher sensitivity to hydrogen gas and a much faster hydrogen desorption rate. It also avoids the need for an external biasing magnetic fi eld which may be important for practical sensor implementation. A wide range of hydrogen gas concentrations has been detected with the nanopatterned material: from 0.1% to 50%, across the threshold of hydrogen fl ammability in air (4%).
We demonstrate experimentally a strong plasmon-assisted enhancement of the transverse magneto-optical Kerr effect in permalloy gratings. The enhanced transverse magneto-optical Kerr effect is accompanied by an increased grating reflectivity with the maximum of enhancement being correlated with plasmonic Fano resonances. This correlation was confirmed by an intuitive Fano model and also through full-vectorial optical simulations. Simultaneously high reflectivity and transverse magneto-optical Kerr effect as well as narrowest ferromagnetic resonance linewidth and vanishing anisotropy make permalloy nanostructures attractive for applications in spintronics and nano-optics such as, for example, all-optical excitation of propagating spin waves and spectral tuning of optical nanoantennas.
The broadband microstrip ferromagnetic resonance technique has been applied for detection and characterization of a magnetic inhomogeneity in a film sample. In the case of a 100nm thick Permalloy film an additional magnetically depleted top sub-layer, practically unidentifiable by the conventional ferromagnetic resonance setup, has been detected and characterized. These results have been confirmed by Brillouin light scattering spectroscopy revealing the fact that the optical properties of the additional sub-layer do not differ much from those of the bulk of the film. Subsequent characterization of a large number of other presumably single-layer films with thicknesses in the range 30-100nm using the same ferromagnetic resonance technique also revealed the same effect.
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