Hyperfine Field Distributions in (ZrCo2)x(ZrFe2)1−x Alloys

Mössbauer-effect measurements in the cubic Laves-phase pseudobinary magnetic alloys (ZrCo2)x(ZrFe2)1−x yield complex spectra. Magnetization curves on these alloys have been previously reported. ZrFe2, with a saturation moment at 4°K of about 1.6 μB per Fe atom and a Brillouin-type magnetization curve, displays a Mössbauer spectrum consisting of two six-line patterns, each with a hyperfine field of about 200 kOe. ZrFeCo has been reported to show only a quadrupole splitting at 78°K, although this is well below the Curie temperature. We have observed resolved hyperfine splitting in this composition at 78°K and at 4°K. The magnetization curves in (ZrCo2)x(ZrFe2)1−x for x=0.2, 0.4, 0.5, and 0.6 imply magnetic-moment distributions. The Mössbauer spectra for these alloys show hyperfine field distributions that are strong functions of temperature over a wide range below the Curie temperatures. Discrete static distributions of hf fields may explain the spectra, but relaxation effects cannot be ruled out.