Optical and Magnetic Studies of CuSeO3·2H2O Based on the Refined Crystal Structure

Abstract

Abstract Magnetic, IR and electronic spectral studies were made on CuSeO3·2H2O, its crystal structure being refined. The IR band at 927 cm−1 was found to be due to a rocking vibration of a water molecule. The H-bonding scheme was suggested. The electronic spectrum shows a maximum of the d-d transition bands at ca. 14000 cm−1. This was explained on the basis of a square pyramidal coordination of a Cu ion. Above 100 K the magnetic susceptibility obeys the Curie-Weiss law with θ=−92·6 K and μeff=2.00βB. At lower temperatures it shows a broad maximum at ca. 45 K, a sharp peak at 26.4 K corresponding to TN. The behaviour could be explained from the antiferromagnetic superexchange interactions of Cu cations through the σ-bonds of SeO32− anions. The small anisotropy and the number of cations intermediated by each anion give rise to the 1-dimensional character. A linear Heisenberg model and the molecular field model gave J⁄k values of −33 and −31 K, respectively. The latter model also gave the observed ratio of |θ|⁄TN.