Evidence of Griffiths Phase Behavior in Paramagnetic State of Heavy Fermion Compounds CexLa1-xB₆ (0.01≤x≤1)

We have investigated the doping-induced changes of magnetic properties of the archetypal heavy fermion compound CeB6 on a series of substitutional solid solutions CexLa1-xB6 (0.01 x 1). For these strongly correlated electron systems high precision measurements of magnetic susceptibility (T ) were undertaken in small external magnetic field aligned along [100], [110], and [111] directions in the simple cubic lattice of these hexaborides. It was shown that for all crystals and all magnetic field orientations the (T ) dependences obey a power law T - at temperatures between 10 and 200 K. The observed critical exponents = 0.77-0.93 demonstrate a monotonous decrease with the increase of Ce content. It is concluded that such a kind of Griffiths phase-type behavior that differs considerably from the convenient Curie-like dependence should be attributed to the emergence of disordered nanometer-size magnetic clusters of Ce-ions in the RB6 matrix.