We report on results of electrical resistivity and structural investigations on the cubic modification of FeGe under high pressure. The long-wavelength helical order (T C 280 K) is suppressed at a critical pressure p c 19 GPa. An anomaly at T X p and strong deviations from a Fermi-liquid behavior in a wide pressure range above p c suggest that the suppression of T C disagrees with the standard notion of a quantum critical phase transition. The metallic ground state persisting at high pressure can be described by band-structure calculations if zero-point motion is included. The shortest FeGe interatomic distance display discontinuous changes in the pressure dependence close to the T C p phase line.

In this paper we report a comprehensive study of the magnetic susceptibility (χ), resistivity (ρ), and specific heat (CP), down to 0.5 K of the cubic CeIn3−xSnx alloy. The ground state of this system evolves from antiferromagnetic (AF) in CeIn3 (TN = 10.2 K) to intermediate-valent in CeSn3, and represents the first example of a Ce-lattice cubic non-Fermi liquid (NFL) system where TN(x) can be traced down to T = 0 over more than a decade of temperature. Our results indicate that the disappearance of the AF state occurs near xc ≈ 0.7, although already at x ≈ 0.4 significant modifications of the magnetic ground state are observed. Between these concentrations, clear NFL signatures are observed, such as ρ(T ) ≈ ρ0 +A T n (with n < 1.5) and CP(T ) ∝ −T ln(T ) dependencies. Within the ordered phase a first order phase transition occurs for 0.25 < x < 0.5. With larger Sn doping, different weak ρ(T ) dependencies are observed at low temperatures between x = 1 and x = 3 while CP/T shows only a weak temperature dependence. PACS. 71.20.Lp Intermetallic compounds -71.27.+a Strongly correlated electron systems; heavy fermions -75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions

Recent studies show that the non-Fermi liquid (NFL) behavior of MnSi and Fe spans over an unexpectedly broad pressure range, between the critical pressure pc and around 2pc. In order to determine the extension of their NFL regions, we analyze the evolution of the resistivity ρ(T ) ∼ A(p)T n at higher pressures. We find that in MnSi the n = 3/2 exponent holds below 4.8 GPa ≈ 3pc, but it increases above that pressure. At 7.2 GPa we observe the low temperature Fermi liquid exponent n = 2 whereas for T > 1.5 K, n = 5/3. Our measurements in Fe show that the NFL behavior ρ ∼ T 5/3 extends at least up to 30.5 GPa, above the entire superconducting (SC) region. In the studied pressure range, the onset of the SC transition reduces by a factor 10 down to T onset c (30.5 GPa) = 0.23 K, while the A−coefficient diminishes monotonically by around 50%.

No abstract