Magnetization and Electrical Resistivity of Terbium Single Crystals

Magnetic-moment measurements have been made on single crystals of terbium (hcp) with fields of 50 to 18 000 Oe applied along the $〈11\overline{2}0〉$ ($a$ axis), $〈10\overline{1}0〉$ (b axis), and $〈0001〉$ ($c$ axis) directions. The temperature range covered was 1.4 to 500°K. The $b$ axis was found to be the easy direction of magnetization with an extrapolated saturation moment of 9.34 Bohr magnetons/atom. Anisotropy was observed in the basal plane below the ferromagnetic Curie temperature but not above. A weak antiferromagnetic state was observed between 229°K and the ferromagnetic Curie point at 221°K. Electrical resistivity measurements were made from 4.2 to 360°K ($a$-axis crystal) and from 4.2 to 300°K ($b$- and $c$-axis crystals). The basal plane curve changed slope at 221 and 229°K. The $c$-axis curve changed slope at 221°K, exhibited a nearly symmetrical maximum about 226°K, and returned to linear behavior near room temperature. The application of a magnetic field of 11 kOe along a $b$ axis caused the pronounced maximum at 226°K to disappear.