Structural ordering in amorphous TbFe₂and YFe₂

Abstract

Total neutron scattering data were collected on sputtered YFe2 at 298 K and TbFez at 423 K with a wavelength of 0"7 A. The TbFe2 data were collected above the magnetic ordering temperature of 383 K. In addition, the elastic neutron scattering of TbFe2 was measured with the use of a pyrolytic graphite analyzer at a wavelength of 1.5/~, and its total X-ray scattering was measured with Mo radiation and a silicon-lithium drifted detector. Experimental radial distribution functions, with statistical error limits, were calculated. Errors due to an incorrect background, scaling of the data and termination effects were minimized. The scale and shape of the experimental background and the coordination numbers, internuclear distances and disorder parameters, for the first six coordination spheres, have been determined. The contribution of paramagnetic inelastic scattering from TbFe2 to the total neutron scattering is quite appreciable. The shape of the background scattering, which goes through a maximum, is indicative of residual coherence and suggests shortrange magnetic ordering where neighboring atom spins are aligned. These effects are not observed in YFe2, nor in the elastic TbFe2 data. The metallic glasses have a structural topology which is quite different from that found in their crystalline analogues. The transition-metal substructure, consisting of corner-sharing tetrahedra, is the only aspect of the crystalline topology preserved in the amorphous phase. The structural parameters suggest a tendency of the rare-earth atoms to cluster, thereby decreasing the number of Fe nearest neighbors relative to the crystalline structure.

Determination of the structural anisotropy in amorphous Tb-Fe films

“…Figure 3 shows the calculated CNs for both Fe and Tb scale proportionately with alloy composition. Although our values appear somewhat low in comparison to electron scattering experiments on Gd-based alloys by Graczyk [23] the trend of our CNs with alloy composition appears to project near-accurate values for the amorphous equivalent of the Laves phase (TbxFel-x: ~4 . anisotropy in the data is most clearly seen as a difference in peakto-peak amplitudes of the fist two periods of EXAFS oscillations.…”

“…Figure 3 is a plot of calculated coordination numbers for the a-TbFe alloys deduced using the EXAFS data acquired with normal incident photons. Values from electron scattering [22,23], x-ray scattering 1241, and neutron scattering 1253 experiments, as well as previous EXAFS studies 126,271 are presented for comparison purposes. The hollow symbols represent the CN of TM atoms around a central TM atom.…”

X-Ray Anomalous Scattering Studies of Fe-Tb Amorphous Thin Films

“…This is because the measured structure factor and the corresponding pair distribution function provide the detailed information about the environmental structure around a certain specified element of alloy systems. Although a number of amorphous thin films were studied extensively, there are a few reports [1,2,3] on structural study of them using X-ray scattering methods. It is because there are many difficulties in sample preparation and measurements in itself as follows: Firstly, scattering intensities from the thin films are very weak, compared to those from the bulk materials.…”