The Non-Resonant Magnetic X-ray Scattering Cross Section of MnF₂. 2. High-Energy X-ray Diffraction at 80keV

Abstract

Results of high-energy non-resonant magnetic X-ray diffraction experiments performed on the model system MnF 2 at a photon energy of 80 keV are presented. A surprisingly high peak intensity of the magnetic 300 reflection of 13 000 photons s -1 in the three-crystal mode and 19 000 photons s -1 in the two-crystal mode, with a peak-to-background ratio of 230:1 and 10:1, respectively, has been achieved. At 80keV, the penetration depth is 7mm. When the path length of the beam through the crystal is varied, the effect of volume enhancement of the intensity diffracted by magnetic reflections is demonstrated. The Q dependence of the magnetic and the charge Bragg reflections has been measured and agrees well with theory. The measurement of the temperature dependence of the sublattice magnetization allows a very accurate determination of the critical exponent/~ = 0.333 (3) and the N6el temperature T N = 67.713 (2) K. Finally, the multiple charge scattering is discussed, which is very pronounced for the magnetic reflections of MnF 2.

High-energy non-resonant X-ray magnetic scattering from EuAs3

“…We also investigated the temperature variation of the lattice spacing close to the magnetic ordering transition and have found a large magnetoelastic anomaly at the lock-in phase transition. The use of high energy (w100 keV) non-resonant X-ray magnetic scattering in investigating the model antiferromagnetic material MnF 2 with 3d ions has been shown recently [1,2]. This technique has several important advantages over the conventional resonant X-ray magnetic scattering technique: (1) it probes the bulk of the material, (2) extinction free measurement of the magnetic intensities of several magnetic reflections is possible, (3) the measured magnetic intensities with low Q can yield the magnetic spin moments S of the scattering ions, (4) high energy X-rays can penetrate sample environment vessels easily.…”

Ho and Fe magnetic ordering in multiferroic HoFe3(BO3)4

“…The completely different behavior of the intensities with temperature is obvious. This can be explained by the element specificity of RXS on one hand and by the simplified magnetic scattering cross-section at high energies 24 for small scattering angles HEXMS probes the component of the spin projected onto the normal of the scattering plane, i.e., along U 2 in Fig. 1.…”

“…In order to have large enough intensities, measurements were performed at the lowest possible position in Q, (0 0 1.5), since the nonresonant x-ray scattering cross-section includes the magnetic form factor, which decreases rapidly with increasing Q. 24 At 100 keV photon energies, the scattering angles are small, i.e., 1.41 • and 4.23 • for the (0 0 1.5) and (0 0 4.5) reflections, respectively. Therefore, an increase in the HEXMS intensity, e.g., with temperature of any reflection along [0, 0, l], directly indicates an increasing magnetic moment perpendicular to the scattering plane.…”

“…At high photon energies the magnetic scattering cross-section does not depend on the polarization of the x rays. 24 …”

Effect of Thermal Diffuse Scattering in Triple-Crystal Diffractometry with High-Energy Synchrotron Radiation

“…On the other hand, the diffracted intensity due to any weak scattering process will increase proportionally to the sample thickness. This has been of great advantage in the study of structural phase transitions (Rfitt et al, 1997;Poulsen et al, 1996) and ground-state magnetic properties of transition metal compounds (Strempfer et at., 1996) by means of highenergy synchrotron radiation. For a model study of the weak thermal diffuse scattering (TDS) in triple-crystal diffractometry with high-energy synchrotron radiation, perfect single crystals are ideal because TDS is enhanced with respect to the integrated reflecting power of the perfect crystal by about the ratio of t/text "~" 100, if a 1 cm-thick crystal diffracts in transmission geometry.…”