OBSERVATION OF SPIN-REDUCTION ANISOTROPY IN THE QUASI-ONE-DIMENSIONALANTIFERROMAGNET CSMNI3

The NMR of Mn-55 in the quasi-one-dimensional noncollinear antiferroma gnet CsMnI3 at T = 1.3 K is investigated in magnetic fields up to simi lar to 40 kOe. Six NMR branches corresponding to six manganese spins p er magnetic unit cell are observed. The NMR spectra correspond satisfa ctorily to the well-known magnetic structure of CsMnI3, taking into ac count the dynamic frequency shift due to the interaction with the low- lying AFMR modes. The average spins [S-A] = 1.86 and [S-B] = 1.74 of t he magnetically nonequivalent Mn2+ ions are determined from the measur ed values of the hyperfine fields. The results obtained agree qualitat ively with the calculations of spin reduction in quasi-one-dimensional antiferromagnets [Y. Watabe, T. Suzuki, and Y. Natsume, Phys. Rev. B 52, 3400 (1995)]. (C) 1998 American Institute of Physics. [S0021-3640( 98)01009-3].