Element-selective X-ray detected magnetic resonance: a novel application of synchrotron radiation

Abstract

X-ray detected magnetic resonance (XDMR) is a new element-selective spectroscopy in which X-ray magnetic circular dichroism is used to probe the resonant precession of spin and orbital magnetization components when a strong microwave pump field is applied perpendicularly to the static bias field. Experimental configurations suitable for detecting the very weak XDMR signal are compared. XDMR signatures were measured in yttrium iron garnet and related thin films on exciting not only the iron K-edge but also the yttrium at diamagnetic sites. These measurements are shown to yield unique information regarding the wide-angle precession of induced magnetization components involving either orbital p-projected densities of states at the iron sites, or spin polarized d-projected densities of states at the yttrium sites. Extending XDMR measurements into the millimeter wave range would make it possible to study paramagnetic systems routinely and investigate optical modes as well as acoustic modes in ferrimagnetic/antiferromagnetic systems.

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.…”

“…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.…”

Beam synchronous detection techniques for X-Ray spectroscopy

“…A new spectroscopy called XDMR, first introduced by J. Goulon in [3], has been developed on ID12. Synchronous detection techniques have extensively been used to measure the extremely weak XDMR signals where several modulations bands are extracted from noise with a vector spectrum analyser (AGILENT 89600 series).…”