Magnetic Properties of DyFe sub 2 H sub 2 from exp 57 Fe, exp 161 Dy Moessbauer Effect and Magnetization Measurements

摘要

A single phase stable hydride with nominal composition DyFe sub 2 H sub 2 is shown to have the cubic C15 Laves structure with a 5% larger lattice constant. exp 57 Fe Moessbauer spectra show two sites with nearly equal population and with different isomer shifts and hyperfine fields. Based on the average hyperfine field at 4.2 K, an Fe moment of approximately 1.6 mu /sub B/ is estimated. From the exp 161 Dy data at 4.2 K, which show a single site, a nearly free-ion moment of 9.8 mu /sub B/ is determined. These results, combined with the total moment of 3.5 mu /sub B/ from bulk magnetization measurements, indicate that the Dy and Fe moments may not be strictly antiparallel in the hydride. Relaxation effects in the exp 161 Dy spectra above 77 K, combined with a sharp decrease in the moment with increasing temperature, imply a weakening of the Dy--Fe magnetic coupling induced by the presence of the hydrogen. (ERA citation 04:023925)