Chapter 94 NMR in intermetallic compounds

The origin of the interesting magnetic properties of GdMn6 Ge6 in the low-temperature, 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 enhancement of the radio-frequency field, suggest the presence of a spiral structure. This information is crucial for a quantitative analysis of the complicated 55 Mn spectra. The anisotropy of the hyperfine field at the 55 Mn site is about 10% and the enhancement has been found to be highly anisotropic, as well. Comparing the temperature dependencies of the Zeeman splitting at the individual lattice sites, Mn has been identified as the source of the transferred hyperfine fields at the 73 Ge nuclei. An analysis of the 73 Ge and 155/157 Gd spectra yields the size and relative orientation of the hyperfine fields and electric field gradients at the nuclei in agreement with 155 Gd Mössbauer spectroscopy results.

Section: Methodsmentioning

confidence: 99%

Section: Appendix E Correction Of Signal Amplitudesmentioning

confidence: 99%

Magnetic structures of GdMn₆Ge₆- a nuclear magnetic resonance analysis

Rösch

Kelemen

Dormann

et al. 2000

“…As expected, the orbital magnetism in the conduction bands was found to be quite weak with orbital moments of about 0.07 µ B at the Mn sites. The isotropic part of the hyperfine field at the 155,157 Gd, 55 Mn, and 73 Ge nuclei was estimated with the known coupling constants [17]. Correct order of magnitude and sign (as far as experimentally known) were obtained, with disagreement in the hyperfine-field ratios for the three Ge sites, however [10].…”

Section: Spin-orbit Interaction and Orbital Magnetismmentioning

confidence: 99%

Spin and orbital polarization in layered rare-earth-manganese ternary intermetallic compounds

Kelemen

Brooks

Dormann

2001

We report the results of ab initio energy-band calculations for the ternary intermetallic compound GdMn6Ge6. The ferrimagnetic arrangement of Gd and Mn magnetic sublattices is reproduced as well as the average moment per Mn atom. The comparatively low strength of the Gd-Mn effective exchange coupling and the occurrence of a weak orbital polarization (3%) at the manganese sites are further results of this analysis. The numerical results are compared with prior magnetization and hyperfine-field analyses.

“…Nuclear magnetic resonance was measured for the same sample in the paramagnetic phase at varied temperature for fixed magnetic field (70 kOe) using a Bruker MSL 300 spectrometer. Due to the non-spherical shape of the powder grains and the cylindrical shape of the sample tube, the demagnetizing field causes a relatively large half width at half height ν 1/2 and a non-negligible part of the 2 D-NMR line peak position's shift δν (plotted with respect to a perdeuterotoluene (PDT) standard in figure 2 and 3) [12,13]. The solid line shown in the ν 1/2 data in the middle part of figure 2 proves the proportionality of the width to the magnetic susceptibility (upper part and equation ( 1)), as must be expected for predominating demagnetization broadening.…”

Section: Experimental Details and Resultsmentioning

confidence: 99%

Magnetic ordering of TbMn₂D₂- a nuclear magnetic resonance analysis

Leyer¹,

Fischer²,

Dormann³

et al. 2001

Nuclear magnetic resonance of 2 D nuclei is measured in the paramagnetic phase of TbMn 2 D 2 powder samples. Static and dynamic contributions of Mn and Tb moments to the nuclear probes are characterized on approach to the ordering temperature T N = 272 K and the possibility of antiferromagnetic correlations between Mn and Tb magnetic moments is analysed. Field and temperature dependence of the magnetization in the ordered state is presented as well.