Observation of spin-reduction anisotropy in the quasi-one-dimensional antiferromagnet CsMnI3

Abstract

The NMR of 55Mn in the quasi-one-dimensional noncollinear antiferromagnet CsMnI3 at T=1.3 K is investigated in magnetic fields up to ∼40 kOe. Six NMR branches corresponding to six manganese spins per magnetic unit cell are observed. The NMR spectra correspond satisfactorily to the well-known magnetic structure of CsMnI3, taking into account the dynamic frequency shift due to the interaction with the low-lying AFMR modes. The average spins 〈SA〉=1.86 and 〈SB〉=1.74 of the magnetically nonequivalent Mn2+ ions are determined from the measured values of the hyperfine fields. The results obtained agree qualitatively with the calculations of spin reduction in quasi-one-dimensional antiferromagnets [Y. Watabe, T. Suzuki, and Y. Natsume, Phys. Rev. B 52, 3400 (1995)].