New phase boundary between magnetic and non-Fermi-liquid in Ce(Rh1-xRux)3B2, for 0≤x≤0.4

A study of the temperature-dependent magnetic susceptibility and electrical resistivity rho(T) (0.5-300 K) on single-phase alloys (CaCu5 type), prepared by argon are melting, reveals a magnetic phase transition with a nonmonotonous decrease of the ordering temperature from T-c = 115 K for x = 0 to T-c approximate to 0 for x = 0.40. A kink in the susceptibility at about 70 K indicates that ferromagnetism (at x < 0.1) transforms to a complex magnetic order for 0.125 less than or equal to x less than or equal to 0.35. Above that concentration rho(T) = rho(0) + AT(n) changes from n approximate to 2 to n approximate to 1.5, a characteristic for non-Fermi-liquid behavior. Under pressure T-c stays almost constant for x = 0.125 but dT(c)/dp grows with increasing Ru content. On the contrary, applied fields up to 12 T do not affect T-c. Low-temperature specific heat and ac susceptibility for x = 0.40 confirm the absence of long-range magnetic order down to 0.5 K, For x = 0.35 C-p/T = 62 mJ/mol K at 1.5 K, a value which is three times larger than that of CeRh3B2. (C) 1998 American Insitute of Physics. [S0021-8979(98)46511-3].