Results

We perfomed a set of NMR measurements in the samples Ca_0.995La_0.005B₆ and SrB₆. In both samples we measured ¹¹B spin-lattice relaxation rates, spin-spin relaxation rates and NMR spectra. Due to the small natural abundance of the isotopes of Ca (0.145%) and Sr (7.02%) with a nuclear magnetic moment and to the very bad sensitivity of these elements it was not possible to find the Ca and Sr signals.

The spin-lattice relaxation rate^4.1 showed in both samples a very surprising and interesting behaviour. In SrB₆ above a certain field dependent temperature T_</I>B the spin-lattice relaxation rate 1/T₁ has been found to be a constant, but field dependent value, while below that temperature 1/T₁ was found to decay very rapidly. In CaB₆ the same temperature dependence has been found, but because of other projects with higher priority, the field dependence has not been measured yet but will be done soon.

The spin-spin relaxation rate 1/T₂ has been found to be of the order of some hundred microseconds and in CaB₆ we found it to vary significantly between different points in the central line.

The NMR spectra showed -- as one would expect -- no Knight shift and no temperature dependence of the quadrupolar splitting. There was almost no difference in the shape of the central line between SrB₆ and CaB₆. The lines of both SrB₆ and CaB₆ and of the reference sample LaB₆ showed only a very small inhomogeneous broadening, what could be seen as a proof for the good quality of the samples.

 

• A short Introduction to Hexaborides
• ¹¹B Spin-Lattice Relaxation
  • Experimental
  • Results
• Spectra
  • Experimental
  • Results
• The Spin-Spin Relaxation Rate
• Discussion
  • Summary

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