EVIDENCE OF SPIN-DENSITY-WAVE TO SPIN-GLASS TRANSFORMATION IN YND ALLOYS

Low-temperature ac and dc magnetic susceptibility and specific-heat me asurements have been carried out on YNd dilute alloys, where the Nd co ncentrations are 1.9, 2.5, 4.5, 6.8, and 9.0 at. %. The most concentra ted alloys (4.5, 6.8, and 9.0 at. %) present long-range antiferromagne tic spin-density-wave (SDW) order below the critical temperature, but some residual frustration is likely to produce a reentrant behavior at low temperatures, where the magnetic data show strong irreversibility effects and the specific heat indicates the occurrence of an anisotro py induced gap near zero frequency in the-density of states of the mag netic excitations. For the less concentrated alloys (1.9 and 2.5 at. % ), thr interacting magnetic state shows typical features of spin-glass behavior. The evolution to this state is ascribed as being due to imp urity disorder and frustration which induces a breaking up of the SDW coherence into small domains.