A-'"D w. WrEDEMAN!o.' J\ (!IlIlIIissiolt fli r Ticjtcmpcratllrjorsc/llmJ;. dcr Baycrischcu A kadem ic dcr l-FissCI'scila/ICIf , ..If unchclI , GUII/awy T he lSolEr hyperfine fields, Er3+ magnetic moments, and electronic spin correlation times in ferromagnetic erbium-al uminum intermetallic structu res have been stud ied between 1.5° and so oK using the Mossbauer effect of the 80.6 keV gamma rays of I"Er. The spin correlation times deduced from both the rale equation model and the Wegener formula follow approximately a T-I temperature dependence below Te. Above Tc the spin correlation times of about 5X 10-11 sec decrease by nearly an order of magnitude and are found to be rather sensitive to the distinct assumptions made on the electronic ground-state multiplet and attributed S: distribution function in the different theoretical approaches.

The hyperfine splitting of the 80.6-keV y transition in Er 166 has been measured in erbium metal between 4.2 ~ and 40 ~ using the M6ssbauer effect. There is evidence for a unique magnetic field and electric fieldgradient at all nuclei in erbium metal. The magnetic field decreases from

No abstract

Nuclear resonant absorption of gamma-rays has been observed in nuclei of Re is7 bound in a crystal lattice. At a temperature of 20 ~ K a small fraction of the gammaquanta of the 134 keV transition to the ground state is emitted with essentially no energy lost to recoil, the recoil momentum being taken up by the entire crystal, not by the individual nucleus. Nuclei of t~e is: similarly bound in a crystal lattice have been irradiated with such gamma-rays emitted without loss of energy, resulting in an oberservable resonance absorption. Using a relative velocity of the order of 10 cm/sec the line emitted with the natural line width has been shifted away from the absorption line, resulting in the destruction of the resonance phenomena. Analysis of the variation in transmission as a function of the Doppler shift of the emitted gamma-ray yields a value of T= (1,5 4-0,2). 10 -11 sec for the lifetime of the 134 keV excited state in Re ~sT.