Anomalous hyperfine field and orbital moment of cobalt in RCo2; R = Pr,Nd, Sm,Gd, Tb,Dy, Ho,Er and Tm

⁵⁹Co spin echo NMR spectra in the magnetically ordered phase of the MgCu₂ type RCo₂ compounds (R = Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm) have been observed. For the RCo₂ with the easy direction of magnetication parallel to the 〈011〉 or 〈111〉 direction, the ⁵⁹Co hyperfine fields at two magnetically inequivalent Co sites are found to be antiparallel, revealing a large anisotropy in the ⁵⁹Co hyperfine field. The results are discussed in terms of a large and anisotropic orbital moment of Co. The transferred hyperfine field due to rare earth spins is estimated from well resolved satellite lines observed in Tb_1?xY_xCo₂. The nuclear quadrupole splitting in the magnetically ordered phase is found to be always larger than that in the paramagnetic phase.