Mössbauer-Effect Study of Single-Crystal Holmium

Abstract

The magnetic structures of holmium metal were studied using the 80.6 keV transition of Er166. Erbium was introduced, as a dilute impurity, into the single-crystal holmium sources through neutron irradiation. Using a cubic, paramagnetic absorber of ErAl3, the intensities of the five magnetic hyperfine lines were studied as a function of temperature. In the ferromagnetic region (T<20°K), a five-line spectrum with a weak central line was obtained when the c axis of the crystal was aligned parallel to the gamma-ray beam. This spectrum is consistent with the ferromagnetic spiral structure determined from neutron diffraction data. The line intensities are insensitive to the distortion of the spiral in which the magnetic moments are grouped symmetrically about the easy directions of magnetization The maximum value of He (at 4.2°K) is the same as in erbium metal. At 20°K the central line was no longer observable, indicating that the magnetic moments are confined to the basal plane at this temperature. The temperature dependence of the internal magnetic field is also reported.