Low-temperature magnetization study on the phase IV ordering in Ce _xLa_1-xB₆ under [111] uniaxial pressures

We have examined the magnetization M of Ce_xLa _1-xB₆ (x = 0.75 and 0.7) under uniaxial pressures P (≤ 100 MPa) applied along the [111] direction, focusing our attention on the enigmatic phase IV ordering where the magnetization is nearly isotropic at an ambient pressure. Under the pressure which stabilizes the phase IV ordering, a cusp is observed upon the phase IV ordering for all directions and a distinct anisotropy is found to develop in the phase IV region as M₁₁₀ > M₁₀₀ > M₁₁₁. These results, combined with the results of a previous uniaxial pressure experiment with P ∥ [110], support the recently proposed Γ₅ type octupolar ordering model.