Novel dynamical properties in the zero-field antiferroquadrupole ordered state of CeB₆

¹¹B-nuclear magnetic resonance (NMR) measurements have been carried out on CeB₆, a prototypical compound for antiferro-quadrupole (AFQ) ordering. NMR spectra were successfully obtained even below 0.1 T where some macroscopic measurements suggest the existence of a new phase boundary. In the AFQ ordered phase, we found a spectral change which should reflect the appearance of additional hyperfine field H_int characteristic of this phase in field. H_int is reduced with decreasing external field. Although the characters at low-fields in the AFQ ordered phase has not been clarified yet, the present experiment shows good possibility that more precise ¹¹B-NMR measurements will open a way to investigate AFQ ordering at very low fields. (author)