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We study the magnetic properties of heavy electrons in Ce(Ru 1− x Rh x ) 2 Si 2 and Ce 1− x La x Ru 2 Si 2 associated with ordering of a spin density wave. One of the short-range orders in CeRu 2 Si 2 is stabilized as a long-range order. Anisotropic gap opening occurs in partial Fermi surfaces below the ordering temperature T N and the rest of the Fermi surfaces contribute to heavy-fermion properties.

H c2 ( T ) has been measured for thin BSCO films at temperatures down to 65 mK and pulsed fields up to 35 T. H c2 ( T ) diverged anomalously as the temperature decreased: at the lowest temperature, it was five times that expected for a conventional superconductor. Although deviations from the conventional behavior have been observed in other superconductors, such strong divergence over such a large range of reduced temperature has not been seen before.

International audience; Abstract : Abstract Capacitance thermometry seems to be the best solution for low-temperature measurements in a high-magnetic field. Vitreous OH-doped silica suits well to this use. A parallel plate capacitor is not very suitable when applied in vacuum, since thermalization against a flat substrate introduces stray-capacitance perturbations. Using vapour deposition of gold, we have prepared an inter-digital pattern of electrodes leaving one face of the slab free. Very small surface area of the electrodes minimizes eddycurrent heating. Relaxation effects could be reduced by careful annealing which removed water molecules from the sample surfaces. Some SiO x layers with controlled OH-content were also prepared by plasma deposition (PACVD).

ZF-μSR measurement on Ce(Ru0.95Rh0.05)2Si2 single-crystalline sample with incident muon beam along both the a- and c-axis showed an exponential relaxation above about TN=2.0 K and two component relaxations were found below 2.0 K. One is a Gaussian relaxation signal which is the precursor of SDW ordering and the other is an exponential relaxation due to the fluctuation of 4f-electron moment. The Gaussian relaxation rate σ increases steeply with decreasing temperature, reflecting the broad field distribution under SDW ordering, and vanishes below 1.8 K. The exponential relaxation rate λ showed critical slowing down with SDW ordering near TN for both a- and c-axis. These behaviors were analyzed by the SCR theory with finite ordering temperature.

We have measured the resistivity of single-crystalline Ce(Ru0.5Rh0.5)2Si2 as a function of an external magnetic field. While this compound is known to show non-Fermi-liquid (NFL) behavior at zero field, we discovered recovery of the conventional Fermi-liquid (FL) behavior above 1 T. It can be considered as the effect of suppression of the spin fluctuations caused by applying a magnetic field. On the other hand, the large positive magnetoresistance is observed at 40 mK which shows rather strong field dependence at low field region (H