HIGH-FIELD MAGNETIZATION OF THULIUM SINGLE CRYSTALS

The magnetization of thulium has been measured along the 101̄0 (b axis) and 0001 (c axis) directions from 4.2 to 300°K in magnetic fields up to 100 kOe. The measurements were taken using a vibrating-sample magnetometer designed and constructed to operate in a 100-kOe superconducting solenoid. The data indicate a Néel temperature of 58°K with large anisotropy favoring the c axis. They suggest that the antiferromagnetic structure below 58°K is an axial structure oriented along the c axis. The low-field isofields for the c axis show that at about 42°K the antiferromagnetic structure begins to square up, and at about 25°K the moments assume ferrimagnetic structure with a net moment along the c axis at 4.2°K of 1.0μB per atom. The ferrimagnetic coupling can be overcome by magnetic fields above 28 kOe, yielding a ferromagnetic structure with a saturation magnetization of 7.14μB per atom. The b-axis sample, however, remained magnetically hard to the highest fields used; at 4.2°K the moment reached 0.75μB per atom at 93 kOe. The data in the paramagnetic region gave a value for μeff of 7.61μB, with paramagnetic Curie temperatures of θ11=41°K, and θ=-17°K, where θ11 is for fields applied along the c axis and θ is for fields applied perpendicularly to the c axis. © 1969 The American Physical Society.