Magnetic Properties of Ce n+1 Co 3n+5 B 2n ( n = 0, 1, 2, and 3) compounds investigated by 59 Co NMR

We have performed 59 Co spin-echo NMR measurements on Ce n+1 Co 3n+5 B 2n ( n = 0, 1, 2, 3) at T= 1.4 K. The NMR spectra corresponding to the inequivalent crystallographic sites were obtained. The resonance frequencies of the 2c-Co have been observed in the range 60-80 MHz, and those of the 6i-Co(6i 1 -Co) around 32 MHz. In addition to the zero-field spectra, the field-swept spectra from non-magnetic Co have also been observed for Ce 3 Co 11 B 4 and Ce 2 Co 7 B 3. These spectra arise from the 3g-Co in Ce 3 Co 11 B 4 and the 6i 2 -Co in Ce 2 Co 7 B 3. From the Co hyperfine field analysis, the Co magnetic moments at the inequivalent crystallographic sites are estimated. Magnitude of the spin moment for the 2c-Co is estimated to be <1.2 μ B for Ce n+1 Co 3n+5 B 2n (n = 0, 1, 2, 3), and to be about 0.4 μ B for the 6i 1 -Co in Ce 3 Co 11 B 4 and Ce 2 Co 7 B 3, while the orbital moment of the 2c-Co varies from <0.3 μ B in CeCo 5 to <0.1 μ B in Ce 2 Co 7 B 3, and those for the 3g-Co and 6i 1 -Co are found to be 0.08 and 0.01 μ B, respectively. The Co magnetic moments are found to be strongly influenced by the crystallographic environment around the Co site.