Magnetic phase diagrams of Ce0.4La0.6B6 up to 15 T investigated by specific heat measurements

Transition temperature between phase I (paramagnetic phase) and II (antifer ro-quadrupolar ordered phase), T-Q, in magnetic fields up to 15 T is invest igated for a high-quality single-crystal Ce0.4La0.6B6 by specific heat meas urements. For H(0 0 1) T-Q increases with magnetic field up to similar to 1 2 T, as is known for larger x. However, T-Q shows a decrease with magnetic held above similar to 12 T, which indicates that phase II closes in the H-T plane, While in H(1 1 0) T-Q continues to increase with magnetic field up to similar to 15 T and remarkable anisotropy of the phase boundary in the h igh-held region is revealed. (C) 1999 Elsevier Science B.V. All rights rese rved.