Abstract: Taking advantage of a novel multiprobe setup we have measured, on a unique sample, the ac-magnetic susceptibility, the resistivity, the ac-specific heat and the thermopower of the superconductor heavy fermion CeCu2Si2 under pressure up to 5.1 GPa. At the superconducting transition temperature Tc, the Meissner signal corresponds to that expected for the sample volume and coincides with the specific heat jump and the resistive transition completion temperatures. Differing from previous observations, here the susceptibility measurements did not reveal any anomaly in the vicinity of the resistive transition onset.

Abstract: We present first results of high-pressure resistivity measurements on pure chromium. Two pieces of evidence show that spin density wave magnetism is suppressed at a critical pressure pc?10GPa, namely, the evolution of the ordering temperature TN(p) and the rapid decrease of the residual resistivity close to pc. Our discussion profits from the comparison between pressurized-Cr and the Cr1-xVx alloy, for which a large amount of information on its electronic properties is available.

Abstract: 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 p and around 2p. In order to determine the extension of their NFL regions, we analyze the evolution of the resistivity ρ(T)˜A(p)T at higher pressures. We find that in MnSi the n=32 exponent holds below 4.8GPa≈3p, but it increases above that pressure. At 7.2 GPa we observe the low-temperature Fermi liquid exponent n=2 whereas for T>1.5K, n=53. Our measurements in Fe show that the NFL behavior ρ˜T 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 Tconset(30.5GPa)=0.23K, while the A—coefficient diminishes monotonically by around 50%.

Abstract: Resistivity of iron under pressure ( p < 17 GPa) has been measured in a new type of Bridgman cell adapted to trap Daphne oil as pressure medium. Here we have done detailed studies on the T -exponent of ? ( T ) in the low p -region of the superconducting phase (13 ? p ? 31 GPa) under magnetic field (? 8 kOe). Very large drop and quasi-complete ? ( T ) transition were observed for the first time in the low- p region of SC-dome. With the increase of magnetic field we obtained, below T SC onset , a trend that the T -exponent is increasing and reached to 1.82 at the highest applied field. Attempt has also been made to estimate the critical current density, which appears to be quite high compared to our earlier work.

Abstract: High pressure electrical resistivity and x-ray diffraction experiments have been performed on Fe single crystals. The crystallographic investigation provides direct evidence that in the martensitic $bcc \rightarrow hcp$ transition at 14 GPa the $\lbrace 110\rbrace{bcc}$ become the $\lbrace 002\rbrace{hcp}$ directions. During a pressure cycle, resistivity shows a broad hysteresis of 6.5 GPa, whereas superconductivity, observed between 13 and 31 GPa, remains unaffected. Upon increasing pressure an electronic instability, probably a quantum critical point, is observed at around 19 GPa and, close to this pressure, the superconducting $T{c}$ and the isothermal resistivity ($0<T<300\,$K) attain maximum values. In the superconducting pressure domain, the exponent $n = 5/3$ of the temperature power law of resistivity and its prefactor, which mimics $T{c}$, indicate that ferromagnetic fluctuations may provide the glue for the Cooper pairs, yielding unconventional superconductivity.