Rapid Suppression of the Metamagnetic Transition for H || ‹111› in NdB₆ by La Doping

Abstract

We have studied the specific heat, magnetization and magnetoresistance of Nd_xLa_1-xB₆ (x=0.9, 0.8, 0.7) single crystals and obtained their magnetic phase diagrams. The antiferro (AF) magnetic phase for H || ‹111› is divided into two phases of AFI below H_c1 and AFII^* (or AFII) above H_c1. In the AFI phase, there exists the component of the parallel magnetic susceptibility up to H_c1. The intermediate metamagnetic AFII phase in NdB₆ disappears already for x=0.9 and in place, new AFII^* phase appears. The AFII^* phase is considered to be the spin-canted phase characterized by the perpendicular magnetic susceptibility. However, the magnetization in the AFII^* phase for x=0.9 and 0.8 exhibits the unusual behavior that the extrapolation of the magnetization curve down to H=0 takes a large negative magnetization value. This unusual behavior disappears at x=0.7. These results indicate that the interaction forming the interamediate metamagnetic AFII phase is rapidly suppressed by the La doping and disappears at x∼0.7.