Abstract
Nuclear hyperfine interactions in Dy metal have been investigated in a temperature range spanning the ferromagnetic, antiferromagnetic and paramagnetic regions (4 2-300 °K), using the Mossbauer effect in 161Dy. The effect was observed in both the 25 6 kev and 74 5 kev γ-ray transitions. No detectable changes in the hyperfine spectra were observed in traversing the ferromagnetic-antiferromagnetic transition. The temperature variations of the effective magnetic field and the electric field gradient at the Dy nucleus are shown to be in fair agreement with a free-ion theory. The ratios of excited-state moments to ground-state moments for both transitions were also measured. For the 25 6 kev transition, values of -1 21±0 02 and +1 01±0 03 were obtained for the magnetic dipole and electric quadrupole moments respectively, and for the 74 5 kev transition similar ratios of +0 84±0 05 and +0 48±0 04 were obtained. Using independently measured values for the ground-state moments we have thus estimated the excited-state moments and compared them with values predicted by nuclear theory.