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Description
Magnetic diffraction using x-ray detected ferromagnetic resonance (DFMR) offers a powerful and novel technique for performing time-resolved measurements on individual spin textures [1,2]. DFMR combines FMR and circular dichroism in REXS as pump and probe, respectively. This allows us to study the element-, layer-, and mode-selective magnetisation dynamics by stroboscopic probing, utilizing the time structure of the synchrotron (∼500 MHz). The radio-frequency field that drives the spin precession is synchronized with the x-ray pulses using the clock of the synchrotron such that each x-ray pulse measures the magnetisation cone at precisely the same point in the precession cycle [3].
We studied the FMR modes of both the conical and field-polarized phases in the chiral magnet Cu2OSeO3 [4]. Following the identification of these modes at different temperatures using broadband vector network analyser FMR, we used DFMR on the crystalline (001) Bragg peak to reveal the time-dependent spin configurations of the selected FMR modes. By being able to measure both the amplitude and phase response of the spin system across the resonance, a continuous phase advance (by 180°) in the conical mode and a phase lag (by −180°) in the field-polarized mode is found. By performing dynamic measurements in the conical phase as a function of the linear polarization angle of the x-rays, i.e., successively probing the dynamics of the moments, we found an inversion of the dynamics along the conical axis upon inverting the applied field direction. By enabling time-resolved measurements of the phase and amplitude of individual magnetic structures, DFMR opens new opportunities for obtaining a deeper understanding of the complex dynamics of chiral magnets.
REFERENCES
1. D. M. Burn, S. L. Zhang, K. Zhai, Y. Chai, Y. Sun, G. van der Laan, and T. Hesjedal. Mode-resolved detection of magnetization dynamics using diffractive ferromagnetic resonance. Nano Lett. 20, 345 (2020).
2. G. van der Laan and T. Hesjedal. X-ray detected ferromagnetic resonance techniques for the study of magnetization dynamics. Nucl. Instrum. Meth. B 540, 85 (2023).
3. G. van der Laan. Time-resolved x-ray detected ferromagnetic resonance of spin currents. J. Electron Spectrosc. Relat. Phenom. 220, 137-146 (2017)
4. D. M. Burn, S. L. Zhang, G. van der Laan, and T. Hesjedal. Time-resolved measurement of spin excitations in Cu2OSeO3. Phys. Rev. B 106, 174409 (2022).
