A NUCLEAR-MAGNETIC-RESONANCE STUDY OF SMCO2

A Co-59, Sm-147 and Sm-149 NMR study of SmCo2 at 4.2 K is reported. Th e Co-59 spin-echo spectrum consists of two lines centered at 44 and 59 MHz. The upper line shows a resolved quadrupole splitting of 1.15 MHz , whereas the lower one is unresolved. The Sm-147 spectrum shows three septets (nuclear spin I-147 = 7/2), two at lower frequencies and one at higher frequencies, with different quadrupole splittings. The resul ts are analysed and related to the presence of magnetically inequivale nt sites corresponding to the easy direction of magnetisation along th e [1 1 1] direction, and the rhombohedral distortion of the crystal la ttice. From the Sm quadrupole splittings the lattice contribution to t he electric field gradient is derived and related to the crystalline e lectric field coefficient A(2)(0) and, thus, to the magnetocrystalline anisotropy due to the lattice distortion. (C) 1998 Elsevier Science B .V. All rights reserved.