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

Rare earth sesquisulfides ?-Tb2S3 and ?-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 ?oH = 18 T. Some step-like transitions have been observed in both compounds. The magnetization of ?-Tb2S3 single crystal under the field along the 6-axis at T = 1.4 K shows a steep increase of about 4.5 ?B, which corresponds to a half of full saturation moment of free Tb3+, at ?oH = 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 ?oH = 0.7 T for H?c and two-step transitions at 0.7 and 1.2 T for H?a are observed. As for ?-Dy2S3, the magnetization curve at T = 1.5 K shows two-step transitions at 1.3 and 1.6 T (H?b), three or four dull steps (H?a or c). The total height of two steps in the M-H curve for H?b corresponds to a half of full Dy3+ moment.