| Research Abstract |
Analyses of internal fields at she nuclear site (observed by NMR), as well as neutron diffraction results, are used to determine magnetic structures of magnetic materials. This is rather classical usage of NMR. However, analyzing procedures are not always simple but careful consideration depending on the material seems to be necessary. Conventional analyses of internal fields sometimes lead to magnetic structures much different from those deduced from neutron diffraction analyses. In particular, such discrepancy is often found in geometrically frustrated systems, where hidden parameters associated with anomalous phenomena may play crucial role. However careful examination of the origin may enable us to find new and essential concept. In this context, we performed various experiments, including NMR and neutron diffraction, for some geometrically frustrated systems and their related compounds, and tired to interpret NMR results reasonably and to understand the nature of the magnetic structure for the frustrated system.
We studied (1) Laves-phase intermetallic compounds such as YMn2, (2) triangular-lattice transition-metal chalcogenides such as BaVS3, (3) tetrahedral cluster transition-metal chalcogenides such as GeV4S8, and (4) other related compounds. Although essential factors are different depending on the material, we found that both dynamic and static anisotropy of the internal field and its temperature dependence are generally remarkable in the frustrated system, indicating that it is quite important to treat these characteristics properly in NMR analyses. Further, from the investigation with use of NMR, neutron diffraction, etc. we proposed new spin and orbital structures for some frustrated systems such as YMn2 and BaVS3.
|
