Magnetic excitations in the paramagnetic phase of a cr‐fe alloy by inelastic neutron scattering

Abstract

The specific topological features of the Fermi surface of chromium have been succesfully used to explain the itinerant antiferromagnetism of chromium as revealed mainly in the neutron diffraction results for chromium and its alloys, Most of these data refer to the static properties of the spin density waves and they were recently summarized in (1) together with the references to the relevant theoretical work. Magnetic excitations i n pure chromium in the antiferromagnetic phase were computed in (2) and (3) for the two-band model for T = 0 K and a linear dispersion relation was obtained. The neutron scattering by magnetic excitations at finite temperatures and in both paramagnetic and antiferromagnetic phase of chromium was treated first by Liu (4) and his results will be used in the present discussion. 0Experimentally the magnetic excitations were recently studied in pure chromium by (5) and (6). in Cr-Mn alloy by (6) and (7), and in Cr-Fe alloy by (8). The common interesting fact found in the above measurements was the presence of a fairly strong inelastic scattering above the Nee1 point extending far into the paramagnetic region.The Cr-Fe system presents a case of special interest. Contrary to other diluents producing the increase of T with increasing electron/atom ratio Fe, Co, and Ni when added to chromium make T decrease. This behaviour is best described in terms of well localized magnetic moments attached to iron impurities interacting with the spin density wave (9, 10). The enhancement in the phonon frequency depression in the region of Kohn anomalies observed in Cr-Fe alloy (11) might also O I ' i g i M t e from this kind of interaction. N N 1 physica (b)