MN55 NUCLEAR MAGNETIC RESONANCE IN MNF2 - SUHL-NAKAMURA INTERACTION

The NMR of Mn55 in antiferromagnetic MnF2 has been reexamined, using both superregenerative and pulsed NMR techniques, in the temperature region 1.3-20A°K. Instead of the single resonance originally reported, five distinct quadrupolar-split transitions are observed, whose separation yields a value of e2qQa=11.7±0.3 MHz. The frequency of the central (1/2 a -1/2) transition extrapolates to 670.38±0.05 MHz at 0A°K. Were there no changes in the hyperfine interaction in going from ZnF2: Mn to MnF2, this would imply ãSzã0S=(99.41±0.03)% in the antiferromagnetic ground state. The magnitude and m dependence of the linewidths of the individual transitions are reasonably consistent with the predictions of the Suhl-Nakamura theory (i.e., the indirect nuclear spin-spin interaction via virtual spin-wave excitations). The failure to observe a transient signal is attributed to the very short T2(<1Aμsec) resulting from the latter interaction. © 1969 The American Physical Society.