Crystal structure and magnetic anisotropy in the magnetic ordered phases of PrB6

We have studied the magnetization and the thermal expansion of PrB6 in both C and IC phases. In the IC phase, the crystal is found to be nearly cubic. This is because the magnitude of <O-xy>(av) is different from site to site in the IC phase. In the C phase, the crystal is easily deformed into the diamond shaped one by a small external field such as a magnetic field or a uniaxial stress along the two-fold axis. This indicates the small AFQ interaction in PrB6. The magnetization exhibits the anisotropy, M((001)) > M-<110> > M-<111> in the IC phase and M-<001> > M-<011> > M-<110> in the C phase. The former is explained by a difference of the domain distribution for three field directions, i.e., the larger the population of the X I configuration, the larger the magnitude of M. In the C phase, the planer type K-xy domain state and the Xperpendicular to configuration are realized for three magnetic field directions. For H parallel to <110> and <111>, the 1-k collinear magnetic structure is realized and the moment is rotated in the xy plane, while for H parallel to <001>, the moment is canted towards z axis from the xy plane. Altough in both cases, Xperpendicular to is associated with the Zeeman energy gain, Xperpendicular to in the former is smaller than that in the latter. This difference makes the anisotropy of M in the C phase as M-<001> > M-<111> > M-<110>.