Magnetic excitations in amorphous Fe75P15C10

Neutron scattering techniques have been used to measure the magnetic excitations in the amorphous ferromagnet Fe75P15C10. Triple-axis measurements show a distinct spin-wave excitation at small momentum transfers that closely obeys a quadratic dispersion relation E=DQ2 for D equal to about 120 meV A2. Time-of-flight polarized-beam measurements made in the vicinity of the first peak in S(Q) near 3-1 show excitations that reach a minimum energy at the maximum in S(Q). These excitations are similar to the roton excitations in He4 except that they are rather broad in energy since they are able to decay into single-particle states. A contour map is presented which shows the scattering measurements in the neighborhood of 3-1 and the results are compared with calculations of magnetic excitations in amorphous systems. © 1977 The American Physical Society.