Small angle magnetic scattering from amorphous DyCu

The unusual magnetic transition previously reported for the random anisotropy amorphous alloy DyCu was investigated by small-angle neutron scattering methods. The measurements were made on two 150-μm sputtered films at the NBSR SANS spectrometer with incident 6.0-Å wavelength, at temperatures between 5 and 77 K, and for wavevectors 0.016≤q≤0.165 Å-1. The small-angle magnetic intensity at fixed q shows a pronounced break at T≅17 K, corresponding to the weak-field susceptibility cusp as measured on the same sample. The lineshapes at all temperatures were observed to be Lorentzian, with a correlation length slowly increasing as T decreases to a maximum of ∼13 Å at 17 K and remaining constant thereafter. These results are compared with susceptibility and specific heat measurements for insight into the proposed mechanism for the transition.