Magnetic structures of GdMn6Ge6 - a nuclear magnetic resonance analysis

The origin of the interesting magnetic properties of GdMn6Ge6 in the low-te mperature, low-field phase is a spiral arrangement of the magnetic moments. This has been established by pulsed nuclear magnetic resonance experiments . Spin-echo spectra taken in an external magnetic field, and the observed e nhancement of the radio-frequency field, suggest the presence of a spiral s tructure. This information is crucial for a quantitative analysis of the co mplicated Mn-55 spectra. The anisotropy of the hyperfine field at the Mn-55 site is about 10% and the enhancement has been found to be highly anisotro pic, as well. Comparing the temperature dependencies of the Zeeman splittin g at the individual lattice sites. Mn has been identified as the source of the transferred hyperfine fields at the Ge-73 nuclei. An analysis of the Ge -73 and Gd-155/157 spectra yields the size and relative orientation of the hyperfine fields and electric field gradients at the nuclei in agreement wi th Gd-155 Mossbauer spectroscopy results.