High field magnetization processes in single crystals of α-Tb2S3 and α-Dy2S3

Rare earth sesquisulfides alpha-Tb2S3 and alpha-Dy2S3 possess orthorhombic crystal structure having two independent rare earth sites. High field magnetization processes for single crystals of these compounds have been investigated up to mu H-0 = 18 T. Some step-like transitions have been observed in both compounds. The magnetization of alpha-Tb2S3 single crystal under the field along the b-axis at T = 1.4 K shows a steep increase of about 4.5 mu(B), which corresponds to a half of full saturation moment of free Tb3+, at mu H-0 = 2.2 T. It is considered that the reorientation of Tb3+ moments on only one Tb site into a ferromagnetic arrangement occurs. When the magnetic field is perpendicular to the b-axis, one-step transition at mu H-0 = 0.7 T for H parallel to c and two-step transitions at 0.7 and 1.2 T for H parallel to a are observed. As for alpha-Dy2S3, the magnetization curve at T = 1.5 K shows two-step transitions at 1.3 and 1.6 T (H parallel to b), three or four dull steps (H parallel to a or c). The total height of two steps in the M-H curve for H parallel to b corresponds to a half of full Dy3+ moment.