Abstract
Using a time-resolved detection scheme in scanning transmission X-ray microscopy (STXM), we measured element resolved ferromagnetic resonance (FMR) at microwave frequencies up to 10 GHz and a spatial resolution down to 20 nm at two different synchrotrons. We present different methods to separate the contribution of the background from the dynamic magnetic contrast based on the X-ray magnetic circular dichroism (XMCD) effect. The relative phase between the GHz microwave excitation and the X-ray pulses generated by the synchrotron, as well as the opening angle of the precession at FMR can be quantified. A detailed analysis for homogeneous and inhomogeneous magnetic excitations demonstrates that the dynamic contrast indeed behaves as the usual XMCD effect. The dynamic magnetic contrast in time-resolved STXM has the potential be a powerful tool to study the linear and nonlinear, magnetic excitations in magnetic micro- and nano-structures with unique spatial-temporal resolution in combination with element selectivity.
Highlights
In spintronics and magnonics, it is important to understand the magnetization dynamics on the micro- and nano-scale e.g., to be able to control the propagation of spin waves
These measurement techniques include but are not limited to: magneto optic Kerr effect (MOKE) [4], Brillouin light scattering (BLS) [5], magnetic force microscopy (MFM) [6], scanning thermal microscopy (SThM) [7], scanning electron microscopy with polarization analysis (SEMPA) [8], and X-ray photoemission electron microscopy (X-PEEM) [9]. For most of these measurement techniques, it is not possible to measure with element selectivity (MOKE, BLS, MFM, SThM and SEMPA), while other measurement techniques like X-PEEM can only probe the surface of the sample with element selectivity
We have shown a way to correctly separate the quantitative pure dynamic magnetic contrast from the background signal in scanning transmission X-ray microscope (STXM)-ferromagnetic resonance (FMR)
Summary
It is important to understand the magnetization dynamics on the micro- and nano-scale e.g., to be able to control the propagation of spin waves. Other measurement techniques have been combined with FMR excitation in order to measure a single nano-sized object in an ensemble These measurement techniques include but are not limited to: magneto optic Kerr effect (MOKE) [4], Brillouin light scattering (BLS) [5], magnetic force microscopy (MFM) [6], scanning thermal microscopy (SThM) [7], scanning electron microscopy with polarization analysis (SEMPA) [8], and X-ray photoemission electron microscopy (X-PEEM) [9]. It is possible to obtain quantitative information about the local precession angle in FMR and its relative phase within a given STXM-FMR experiment
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