HYPERFINE INDUCED MAGNETIC ORDER IN PR - NEUTRON-DIFFRACTION AT MK TEMPERATURES

With elastic neutron scattering we investigated the magnetic reflectio ns of a single crystal of pure Pr in the temperature range down to 8 m K. We found a double peak structure consisting of a narrow antiferroma gnetic satellite with incommensurable wave vector and a broad peak of presumably quasielastic origin, as seen in previous measurements at hi gher temperatures. The saturation of the magnetic moment is almost rea ched at the lowest temperatures and approaches the theoretical expecte d value of 0.6 mu(B). Below a temperature of T = 40 mK the magnetic mo ment turns away from the b-axis towards the a-axis of the crystal. Mea surements in-an external magnetic field indicate 3 domains. A magnetic field along the a-axis bigger than 500 mT destroys the magnetic order .