Abstract: 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].

Abstract: The growing valency of the Yb ion, when Cu is substituted by Al in YbCu5 – xAlx, causes a magnetic instability at a critical concentration x(cr) approximate to 1.5. Alloys in the vicinity of x(cr) exhibit typical non-Fermi-liquid properties. (C) 1999 Elsevier Science B.V. All rights reserved.

Abstract: We report on a series of structural, magnetic, and thermodynamic measurements, a study of transport properties and x-ray absorption edge spectroscopy on Ce(Rh1-xRux)(3)B-2. These investigations evidence that in addition to the already established ferromagnetic range for x less than or equal to0.06, a complex antiferromagnetic structure exists for concentrations 0.1 less than or equal tox less than or equal to0.35. The behavior in the latter regime is dominated by an extraordinary strong intersite coupling; however, the magnetic moments involved appear to be very small. At the phase boundary to the paramagnetic regime (x approximate to0.4), significant deviations from a Fermi-liquid behavior occur.

Abstract: Magnetic, transport, and thermal properties of CeCu2Mg are investigated to elucidate the lack of magnetic order in this heavy-fermion compound with a specific heat value, Cmag/T|T→0≈1.2 J/mol K2 and robust effective magnetic moments (μeff≈2.46μB). The lack of magnetic order is attributed to magnetic frustration favored by the hexagonal configuration of the Ce sublattice. In fact, the effect of magnetic field on Cmag/T and residual resistivity ρ0 does not correspond to that of a Fermi liquid (FL) because a broad anomaly appears at Tmax≈1.2 K in Cmag(T)/T, without changing its position up to μ0H=7.5 T. However, the flattening of Cmag/T|T→0 and its magnetic susceptibility χT→0, together with the T2 dependence of ρ(T), reveal a FL behavior for T≤2 K which is also supported by Wilson and Kadowaki-Woods ratios. The unusual coexistence of FL and frustration phenomena can be understood by placing paramagnetic CeCu2Mg in an intermediate section of a frustration-Kondo model. The entropy, Smag, reaches 0.87Rln6 at T≃100 K, with a tendency to approach the expected value Smag=Rln6 of the J=5/2 ground state of Ce3+.