ON THE MAGNETIC-INTERACTIONS IN METAL-BE-13 COMPOUNDS

We report magnetization, Mossbauer, and neutron experiments to determi ne the low-temperature magnetic structure of the heavy-fermion compoun d NpBe13. The magnetic wave vector is q = [1/3 0 0], and nearest neigh bor moments are oriented perpendicular to each other. We have found an unusual modulation of the moments, which reflects the influence of th e strong Kondo interaction. Comparisons are made with the magnetic arr angements found in the rare-earth Be-13 compounds, and it is concluded that a search for magnetic correlations in UBe13 should be concentrat ed around this wave vector.