Abstract
<sup>195</sup> Pt-, <sup>139</sup> La- and <sup>11</sup> B-NMR have been investigated in quaternary RM <sub>2</sub> B <sub>2</sub> C (R=Y, La, Th and M=Ni, Pd, Pt). The electric quadrupole frequency of <sup>139</sup> La changes more than 5 times in magnitude from M=Ni to Pt, indicating that the hybridization of La-5d and d-electrons of M-element changes largely. The analysis of <sup>11</sup> B and <sup>139</sup> La spectra shows also the large change of the magnetic anisotropy with R and M element, i.e., χ <sub>∥ c</sub> >χ <sub>∥ ab</sub> in LaNi <sub>2</sub> B <sub>2</sub> C, but χ <sub>∥ c</sub> <χ <sub>∥ ab</sub> in YNi <sub>2</sub> B <sub>2</sub> C. The data of T <sub>1</sub> T and K of <sup>195</sup> Pt and <sup>11</sup> B are consistent with the band effects and with no evidence of strong antiferromagnetic correlation effects. © 1996 Plenum Publishing Corporation.