The sign and magnitude of the magnetic hyperfine field in the Ni spinels NiFe2O4, NiCr2O4, NiFe0.3Cr1.7O4, NiRh2O4, and GeNi2O4 were determined by means of 61Ni Mössbauer spectroscopy in external magnetic fields. The hyperfine fields of Ni2+ ions in octahedral lattice sites are negative and of the order of −10 T, and positive for Ni2+ at tetrahedral sites ranging from +2.5 T in NiRh2O4 up to +63 T in NiFe0.3Cr1.7O4. The sign and magnitude of the hyperfine fields are explained in the frame of ligand field theory including the effects of 3d–4p orbital mixing.

The hydrogen storage material LaNi5 has previously been shown to degrade into LaH2 and (presumably) Ni metal on repeated absorption and desorption of hydrogen. 61Ni Mössbauer measurements show directly the presence of nickel microprecipitates in severely degraded material.

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Abstract.We have used an optical pumping-Zeeman scanning technique in order to determine the isotope shift in the 3,261 A resonance line of 43-day, spin-ll/2 l~SmCd. A sample of ~ 5 x 10 ~2 atoms was aligned in the IS 0 diamagnetic ground state by optically pumping the sample with one selected Zeeman-scanned component of the 3P a -3,261 A resonance line from a 11~Cd lamp. The alignment was detected through the modulation of the pumping beam at the nuclear resonance frequency. Thus by Zeeman scanning the F = 9/2 component of the 3P 1 level and using previously determined A-and B-values, we find 6v(l14-115m(9/2))= -4,234(48)MHz and t~4Cd-atsmCd isotope shift=87(48)MHz. We calculate a staggering parameter ?(ltS~Cd)=0.73(26), and a change in mean-square nuclear charge radius 6 (r2) 114' 115m =0.035 (18) fm 2.