Abstract
Collective spin excitations of ordered magnetic structures offer great potential for the development of novel spintronic devices. The present approach relies on micromagnetic models to explain the origins of dynamic modes observed by ferromagnetic resonance (FMR) studies, since experimental tools to directly reveal the origins of the complex dynamic behavior are lacking. Here we demonstrate a new approach which combines resonant magnetic X-ray diffraction with FMR, thereby allowing for a reconstruction of the real-space spin dynamics of the system. This new diffractive FMR technique builds on X-ray detected FMR that allows for element-selective dynamic studies, giving unique access to specific wave components of static and dynamic coupling in magnetic heterostructures. In combination with diffraction, FMR is elevated to the level of a modal spectroscopy technique, potentially opening new pathways for the development of spintronic devices.
Highlights
Collective spin excitations of ordered magnetic structures offer great potential for the development of novel spintronic devices
Synchrotron radiation-based X-ray detected ferromagnetic resonance (FMR) (XFMR) was developed to study element-specific magnetization dynamics, giving layer-selective resolution of the magneto-dynamics in multilayer samples.[9−19] Magnetic and chemical contrast is provided by the X-ray magnetic circular dichroism (XMCD) effect,[20,21] while the phase difference between the spin precessions can be determined using stroboscopic sampling
Using the rich magnetic structure of a Y-type hexaferrite as an example, we demonstrate the capabilities of diffractive ferromagnetic resonance (DFMR)
Summary
Scope (STXM),[22] on the other hand, allows for the detection of FMR modes with a spatial resolution down to a scale of ∼25 nm.[23]. The DFMR signal follows a sinusoidal behavior as a function of the time delay between the X-ray pulse arrival time (probe) and the RF (pump) The period of this oscillation is 166 ps, corresponding to the 6 GHz RF field applied to the sample. DFMR measures the variation in intensity of the scattered peaks resulting from the stroboscopic probing of the magnetic structure with a pulsed X-ray source synchronized with magnetic dynamic processes For this purpose, we used the 900-bunch operation mode at the Diamond Light Source, providing pulsed photon bunches (41.5 ± 0.2) ps FWHM at a repetition frequency of the synchrotron master clock (499.68 MHz).[37] For the stroboscopic measurements, the microwave frequency has to be a harmonic of the X-ray pulse frequency, the resonance is driven at multiples of the clock frequency, corresponding to a ∼2 ns interval between consecutive X-ray pulses. Burn: 0000-0001-7540-1616 Young Sun: 0000-0001-8879-3508 Gerrit van der Laan: 0000-0001-6852-2495 Thorsten Hesjedal: 0000-0001-7947-3692
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