Double-resonant x-ray and microwave absorption: Atomic spectroscopy of precessional orbital and spin dynamics

Abstract

We show that double-resonance spectra recorded during the simultaneous absorption of x-ray and microwave ͑MW͒ photons are a fingerprint of the perturbed electronic configuration of atomic species driven to ferromagnetic resonance. X-ray absorption measurements performed as a function of x-ray energy and polarization over the Fe L 2,3 edges of single-crystal yttrium-iron garnet reveal MW-induced multiplet features related to angular momentum transfer from the MW field to localized Fe 3d magnetic sublevels. O K-edge absorption spectra demonstrate the formation of dynamic 2p-orbital magnetization components at O sites coupled to the Fe magnetic moments at tetrahedral and octahedral sites. These results are compared with double-resonance x-ray absorption spectra of Permalloy, showing that the MW transition probability is distributed according to the hybridization character of the 3d states and proportional to the unperturbed unoccupied magnetic density of states of metals and insulators.

Longitudinal detection of ferromagnetic resonance using x-ray transmission measurements

“…1,5,6,8,9,12,14,15,17 Ferromagnetic resonance signals have been observed at energies from 500 eV to 7 keV on the following atoms: Fe ͑L 3 / L 2 -edges and K-edge͒, Ni ͑L 3 / L 2 -edges͒, Co ͑L 3 / L 2 -edges͒, Gd ͑M 4 / M 5 -edges͒, Y ͑L 3 / L 2 -edges͒, O ͑K-edge͒, and Tb ͑M 5 -edge͒. These experiments allowed element-specific studies of the magnetization precession in ferromagnetic 2,8,9 and ferrimagnetic 3,10,11,13,16 compounds as well as measurements of the relative phase and precession angle of the magnetization in coupled metal layers. 6,8,9,14,15,17 XFMR experiments have revealed, e.g., the precession of induced magnetic moments of nonmagnetic species such as Y and O in the ferrimagnetic oxide Y 3 Fe 5 O 12 .…”

“…Successful experiments of x-ray detection of ferromagnetic resonance ͑XFMR͒ have been carried out on metal films and multilayers ͓Ni 80 O 12 ͑Ref. 10͔͒, using either fluorescence, [2][3][4]8,10,11,13,16 reflectivity, 2,8 or transmission measurements. 1,5,6,8,9,12,14,15,17 Ferromagnetic resonance signals have been observed at energies from 500 eV to 7 keV on the following atoms: Fe ͑L 3 / L 2 -edges and K-edge͒, Ni ͑L 3 / L 2 -edges͒, Co ͑L 3 / L 2 -edges͒, Gd ͑M 4 / M 5 -edges͒, Y ͑L 3 / L 2 -edges͒, O ͑K-edge͒, and Tb ͑M 5 -edge͒.…”

“…6,8,9,14,15,17 XFMR experiments have revealed, e.g., the precession of induced magnetic moments of nonmagnetic species such as Y and O in the ferrimagnetic oxide Y 3 Fe 5 O 12 . 11,16 Further, it has been pointed out that XFMR may potentially be used to quantitatively determine dynamic changes of the spin and orbital magnetization using the x-ray magnetic circular dichroism ͑XMCD͒ sum rules. 2,10,11,16,17 Most XFMR measurements to date have been carried at fixed x-ray photon energy.…”

“…11,16 Further, it has been pointed out that XFMR may potentially be used to quantitatively determine dynamic changes of the spin and orbital magnetization using the x-ray magnetic circular dichroism ͑XMCD͒ sum rules. 2,10,11,16,17 Most XFMR measurements to date have been carried at fixed x-ray photon energy. Recently, however, x-ray absorption spectra have been measured with microwave excitations in magnetic resonance conditions over an entire absorption edge, opening an unconventional possibility to apply the sum rules.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Element sensitivity is obtained by choosing the x-ray photon energy corresponding to a core-to-valence band transition of the atom under investigation. The relatively large separation between the absorption lines of the different elements at the x-ray energies of interest as well as the x-ray absorption line shape dependence on the type and position of neighbor atoms allows one to study the magnetic properties of each element separately in well defined environments.…”