Magnetic Moments and Hyperfine Interactions in Carbon-Stabilized Fe5Si3

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Abstract
Powder samples of the intermetallic compound Fe5Si3 which are stable at room temperature have been prepared by the addition of small quantities of carbon. They have been studied by x-ray, Mössbauer, and neutron-diffraction techniques. The structure remains essentially of the D88 type with 4FeI and 6FeII atoms in the hexagonal unit cell. The material is ferromagnetic with a Curie temperature of 112°±2°C. The Mössbauer spectra show a complex hyperfine pattern which is sensibly constant between 77° and 4.2°K and which can be analyzed as a superposition of a set of six sharp lines corresponding to a hyperfine field of 137 kOe on a more diffuse spectrum corresponding to a large hyperfine field. An estimate of the areas under two spectra is consistent with the smaller field being associated with FeI. The absorption by FeII nuclei shows that they are not all equivalent and have hyperfine fields ranging between 180 and 242 kOe. The FeI spectra show an axially symmetric quadrupole splitting of 12e2Qq = +0.35 mm/sec. Neutron diffraction measurements at 4.2°, 100°, 290°K, and 150°C confirm that the spin direction is parallel to the haxagonal axis, and show that the magnetic moments are FeI = 1.05±0.15 μB, FeII = 1.55± 0.15 μB.

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