Magnetism in α-R2S3 (R = Pr and Nd) single crystals

Magnetic susceptibility, chi, and specific heat, C, of the isostructural rare-earth sesquisulfides alpha-R2S3 (R = Pr and Nd) have been investigated on single crystals. The chi(T) of alpha-Nd2S3 shows a broad peak around 3.5 K when a magnetic field of 100 Oe is applied along the b-axis of the orthorhombic crystal structure. A Neel temperature T-N above 2 K has been determined as 2.75 K by an inflection point in the chi(T) and a sharp peak in the C(T). Furthermore, the C(T) indicates another peak at around 0.65 K. The ground states of Nd3+ on both the two Nd sites are concluded as Kramers doublets. The chi(T) of alpha-Pr2S3 shows a broad peak around 3.8 K only in the case of H//b. The chi for H perpendicular to b is almost constant below 5 K, which suggests existence of Van Vleck paramagnetic contribution. An inflection point in the chi(T) (H//b) exists at T-N = 2.95 K which is consistent with the temperature of a sharp peak observed in the C(T). A Schottky-type anomaly around 8 K in the C(T) has also been found. The ground states of Pr3+ on two Pr sites are considered as a pseudo-doublet and a singlet.