Spin excitations in laser-molecular-beam epitaxy grown nanosized YIG films: towards low relaxation and desirable magnetization profile

摘要： We describe synthesis of nanosized Y3Fe5O12 (YIG) films grown by laser-molecular-beam epitaxy on Gd3Ga5O12 (GGG) and Nd3Ga5O12 (NdGG) substrates with (111) orientation and present results of ferromagnetic resonance (FMR) and spin wave propagation studies in these heterostructures. It is found that magnetic parameters of YIG films grown on NdGG and GGG substrates are considerably different. FMR spectra of YIG/NdGG structures are characterized by a large number of narrow peaks, while FMR spectra of YIG/GGG structures consist of a small number of peaks or one peak. The effective magnetization of YIG films grown on NdGG substrates is less than that of YIG films grown on GGG and is more sensitive to the growth conditions. A lateral inhomogeneity of YIG/NdGG structures is observed in spin wave propagation experiments. For YIG/NdGG and YIG/GGG structures the FMR linewidth ?H of a single peak sharply increases with temperature decrease from 298 to 67 K. The observed increase of ?H is explained by typical relaxation processes caused by the presence of Fe2+ ions. From the spin-wave propagation study it is also found that relaxation of spin-waves explains only a minor part of the FMR single peak linewidth in YIG/NdGG structures. On the basis of obtained results, YIG/GGG/semiconductor- and YIG/NdGG/semiconductor-heterostructures with expected low spin-wave relaxation and desirable effective magnetization profile are proposed.