Magnetic-resonance exchange scattering at the ironLIIandLIII

Abstract

Specular reflectivity of p-polarized light near the iron L\\ and L\u absorption edges was measured from a single-crystal iron film with an external magnetic field perpendicular to the scattering plane. Large changes in reflectivity were observed upon reversal of the direction of the magnetic field. We attribute this resonant magnetization-sensitive effect to the interference between magnetic and nonmagnetic contribution to the resonant scattering. Similar effects can be expected in other ferromagnetic and ferrimagnetic systems. PACS numbers: 78.70.Ck, 75.25,+z, 76.90.+d X-ray scattering has become an important experimental technique in the investigation of magnetic materials. ] Of particular importance is the recently observed large resonant enhancement of the magnetic scattering cross section near an absorption threshold. 2,3 In favorable cases the magnetic scattering cross section can be comparable to that of charge scattering. For example, measurements in holmium by Gibbs et al. 1 have shown an enhancement of over fifty in the magnetic satellite intensities as the photon energy is tuned across the L\\\ edge (2/73/2 to 5d, 8.067 keV). Similar experimental studies at the Af iv and My edges of UAs (3d 3 /i to 5/, 3.728 keV and 3^5/2 to 5/, 3.552 keV, respectively) by Isaacs et al. 3 have demonstrated even larger resonant enhancements of magnetic Bragg reflections. At the M\\ edge the scattering intensity of the (0,0, f ) reflection is 1% of the intensity of the (0,0,2) charge reflection, which is an enhancement of 7 orders of magnitude over the magnetic scattering intensity measured far from the edge. These observations can all be explained by resonant exchange scattering, 4 in which large resonant enhancements result from strong electric multipole transitions from atomic core levels to unoccupied states above the Fermi level, with the magnetic sensitivity arising both from the spin polarization of the partially occupied states and from exchange splitting of the unoccupied states.The previous work 2,3 on Ho and UAs studied the energy dependence of Bragg peaks in these antiferromagnetic structures which are purely magnetic in origin. For the 3d transition metals large resonant enhancements are predicted for the Lnjn edges. 4,5 In these materials, however, the transitions all occur at wavelengths which are outside the limiting sphere for Bragg reflections. However, measurement of the specular reflectivity (which is not restricted in wavelength) from ferromagnetic or ferrimagnetic samples should also be sensitive to resonant exchange scattering. In this work, we measure the specular reflectivity utilizing a linearly polarized photon beam with its polarization vector in the scattering plane (p-polarized light), and an external magnetic field perpendicular to the scattering plane.The effect of resonant exchange scattering is manifested as changes in the specular reflectivity upon reversal of the direction of the magnetic field. 6 To illustrate the effect better, an asymmetry ratio R defined as was derived as a functi...

Antiferromagnetic dipolar ordering in[Co2MnGe∕V]Nmultilayers

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Soft x-ray resonant magneto-optical Kerr effect as a depth-sensitive probe of magnetic heterogeneity: Its application to resolve helical spin structures using linear p polarization

“…It should be noted that the I K spectra of the p-polarized soft x rays, as a function of in the vicinity of the resonance edges, provide invaluable information on such depth-varying spin structures. 10,11 We replot the I asy spectra in the left panel of Fig. 1(d), for the L series of different pxL, pyL, nxL, and nyL orientations with respect to a fixed pxR orientation.…”

“…9 Visible light or x-ray magneto-optical (MO) effects, such as the Kerr rotation K and ellipticity K , have been widely used to investigate a rich variety of magnetic states in magnetic heterostructures, because the MO effect is significantly sensitive to the small amount of magnetic moments in their magnitude and direction. [10][11][12][13][14][15][16] In particular, a synchrotron x-ray MO spectroscopy is emerging as a powerful cuttingedge technique, becoming a popular method to investigate the various magnetic properties being associated with nanostructures because of its several unique characteristics such as element specificity, magnetic sensitivity, and large resonant enhancement in the vicinity of the absorption edges, as well as the ongoing growths in the measurement and/or analysis techniques. [13][14][15][16][17][18] Specifically, the K and K spectra, as a function of the grazing angle of incidence for different photon energies h s near the resonance regions, provide invaluable information on magnetic heterostrutures, such as depth-varying spin directions, so that these spectra are very informative to determine the depth-dependent spin structure inherently present in the magnetic multilayer films that consist of several ultrathin layers of different elements.…”

RASOR: An advanced instrument for soft x-ray reflectivity and diffraction

“…Soft x-ray scattering experiments were first undertaken over 20 years ago, with an in-vacuum diffractometer designed for studying multilayer films. 4 The first scattering experiment at a transition metal L edge was performed by Kao et al, 5 on a single crystal of Fe͑110͒, directly testing the prediction by Hannon of a large resonant enhancement. 6 By measuring the reflectivity from the sample, and constructing a model of the reflectivity, they were able to demonstrate that their measurements were sensitive to the magnetic parameters calculated for iron.…”