Exploring the Magnetic Susceptibility of a Haldane Compound Sm $$_{2}$$ 2 BaNiO $$_{5}$$ 5 : Optical Spectroscopy of Sm $$^{3+}$$ 3 + Kramers Doublets

An optical spectroscopic study of quasi-Haldane chain nickelate Sm 2 BaNiO 5 is presented. A temperature-dependent splitting of the ground-state Kramers doublet of the Sm 3 + ion due to an antiferromagnetic ordering at T N = 55 K has been obtained experimentally and used to calculate the Schottky-type anomaly in magnetic susceptibility. The value of the magnetic moment of Sm 3 + ion at zero temperature has been estimated within the model of the ground doublet. One-dimensional magnetic behavior of the nickel subsystem is emphasized.