29Si nuclear magnetic resonance and relaxation in the paramagnetic state of CeCu 2Si 2

Abstract

29Si nuclear magnetic resonance (NMR) and relaxation studies of the unstable-moment compound CeCu 2Si 2 have been carried out to probe the electronic state of the nearly-trivalent Ce ions. Isotropic and anisotropic NMR shifts indicate effects of both crystalline electric fields (CEF) and low-temperature moment reduction on the Ce ionic states. A relatively large anisotropic shift was observed at low temperatures, and also obtained from a CEF-state calculation in the molecular-field approximation. The hyperfine coupling also appears to be anisotropic, although this is not manifested in the temperature dependence of the shift due to changing CEF-state populations. NMR estimates of the Ce-spin fluctuation time vary with temperature in a manner similar to the neutron quasielastic scattering linewidth at high temperatures, but suggest the onset of spatially coherent fluctuations.