Site-Specific Studies on X-Ray Magnetic Circular Dichroism at Fe K Edge for Transition-Metal Ferrites

Abstract

Experiments on X-ray magnetic circular dichroism (XMCD) were performed with synchrotron radiation for Zn and Mn-Zn ferrites (normal-spinel structure) and Ni, Co and Cu ferrites and magnetite (inverse-spinel structure). The inverse-spinel ferrites have positive-to-negative dispersion-type XMCD signals in the pre-edge region of the Fe K edge, which originate from Fe 3+ ions in the A sites. There are no such signals for normal-spinel ferrites. Two kinds of negative-to-positive dispersion-type XMCD signals were observed in 7.119-7.125 keV and 7.122-7.129 keV regions of the main edge, which are caused by a mixture of Fe 3+ and Fe 2+ ions of the B sites in magnetite and Fe 3+ ions of the B sites in the other inverse-spinel ferrites, respectively. The B-site origin of the XMCD main-edge spectra was also confirmed by observation of X-ray resonant magnetic scattering for the 222 reflection of Ni ferrite.

Investigation of pressure-induced magnetic transitions in CoxFe3−xO4Subı́as1, Cuartero2, Garcı́a3 et al. 2013Phys. Rev. B314160View full textAdd to dashboardCite

“…These spectra are similar to previously reported ones. 17,[25][26][27] In spite of the difference in the Fe content, the energy line shape of the XANES spectra closely resembles each other in both pre-edge and main-edge regions, as shown in Fig. 2 Figure 2(b) shows the Fe K-edge XMCD spectra in this series.…”

“…All the spectra show two dispersion-type XMCD signals at the pre-edge and the main-edge regions, respectively, showing opposite signs. XMCD experiments at the Fe K-edge for Mn and Mn-Zn normal-spinel ferrites do not show the positive-to-negative dispersion-type signal in the pre-edge region, 26,27 which indicates that the prepeak signal mainly originates from Fe 3+ atoms in the tetrahedral A sites. Starting from CoFe 2 O 4 and increasing the Co content, the amplitude of the XMCD signal at the pre-edge decreases in agreement with the decrease of the occupancy of Fe 3+ in the A sites ( Fig.…”

Parity and Time-Reversal Breaking Effects on Resonant X-ray Scattering at the Fe Pre-K-Edge in Magnetite

“…3 shows the calculated absorption spectra in comparison with the experiment. 36 Any reliable theoretical estimates of the core-level energy are not available.…”

“…3 shows the calculated XMCD spectra in comparison with the experiment. 36 The calculated difference is divided by the value at the peak of the main edge in the absorption coefficient. Since no scale is shown for the XMCD spectra in ref.…”

Site-specific magnetization reversal studies of magnetite

“…In Nd 2 Fe 14 B, it was found, for instance, that the ͓001͔ easy axis of magnetization arises predominantly from one of two nonequivalent sites. 13 Previous researchers have performed site-specific x-ray magnetic circular dichroism on ferrite powders 14 and crystals, 15 but to our knowledge, measurements have not been performed to examine how the magnetic moments of octahedral and tetrahedral sites in crystals of magnetite individually respond to reversal of applied magnetic field. We have performed magnetic-sensitive DANES studies at Bragg reflections that separate the nonequivalent sites to obtain site-specific magnetic field-reversal loops.…”