Figure : Variable-temperature 31 P NMR spectra of Bi 0.852 P 0.148 O 1.648 obtained at 16.4 T at a spinning rate of 4 kHz, with a recycle delay of 30 s. At room temperature, the 31 P NMR spectrum shows a single highly broadened feature similar to the 51 V NMR spectra of Bi 0.913 V 0.087 O 1.587 . A narrowing isotropic linewidth is seen with increasing temperature that reveals four distinct 31 P resonances.