Condensed-Matter Physics & Materials Science Seminar

Nanoscale patterned magnetic structures and multi-component magnetic devices have been studied actively for applications such as highly efficient data storages, non-volatile magnetic memory devices and magnetic sensors. Those studies demand high resolution magnetic imaging tools which can characterize complex, often buried nanoscale structures. Ferromagnetic Resonance (FMR) is a powerful spectroscopic tool which presents quantitative characterization of magnetic parameters. FMR using Magnetic Resonance Force Microscopy (MRFM) is an excellent tool for the study of ferromagnetic nano-structures based on its high sensitivity and high resolution. However, for ferromagnetic materials, it is difficult to achieve a spatially well-resolved FMR signal due to the strong spin-spin interactions which lead to collective spin wave excitations, reflecting the global rather than local properties of a sample.
In this talk I will present our recent demonstration of localized FMR modes and their use for FMR imaging [1]. Using a variational method with a simple model of particle wavefunctions in a quantum well we obtain a quantitative understanding of the mechanism of localized modes created by means of a strong inhomogeneous probe tip field. This new magnetic resonance imaging technique enables us to map the internal magnetic fields and dissipations in various ferromagnetic structures with the demonstrated high spatial resolution ~200 nm and high field sensitivity ~ 1 G/Hz1/2 in the detected volume of ~ 5 × 10−21 m3.
[1] “Nanoscale scanning probe ferromagnetic resonance imaging using localized modes”, Inhee Lee, Yuri Obukhov, Gang Xiang, Adam Hauser, Fengyuan Yang, Palash Banerjee, Denis V. Pelekhov, and P. Chris.Hammel, Nature 466, 845 (2010).