Magnetic hyperfine interactions in Sm149 in ferromagnetic SmAl2

Abstract

The internal field acting at the samarium nucleus in SmAl2 is investigated theoretically and experimentally. The internal field is computed in the molecular field approximation assuming a crystalline electric field to act on the trivalent samarium ion. Admixtures of the first excited multiplet of the ion by the exchange and crystalline electric field are included in the calculation and lead to an increase of no more than 10% in the theoretically predicted internal field from the values predicted when the admixture is neglected if a crystal field interaction of reasonable size is assumed. The internal field resulting from theory is compared with the values resulting from Mossbauer studies of the hyperfine structure of the 22 kev gamma transition in Sm149. The best fit made to the experimentally observed Mossbauer absorption patterns leads to an internal field much smaller than that predicted by theory. Possible sources of this disagreement between theory and experiment are discussed.