Quantum criticality near the upper critical field of Ce2_2PdIn8_8

We report low-temperature specific heat measurements in magnetic fields up to 12 T applied parallel and perpendicular to the tetragonal c-axis of the heavy fermion superconductor Ce$_2$PdIn$_8$. In contrast to its quasi-two-dimensional (2D) relative CeCoIn$_5$, the system displays an almost isotropic upper critical field. While there is no indication for a FFLO phase in Ce$_2$PdIn$_8$, the data suggest a smeared weak first-order superconducting transition close to $H_{c2}\approx 2$ T. The normal state electronic specific heat coefficient displays logarithmically divergent behavior, comparable to CeCoIn$_5$ and in agreement with 2D quantum criticality of spin-density-wave type

Search for quantum criticality in a ferromagnetic system UNi1-xCoxSi2

Polycrystalline samples of the isostructural alloys UNi1-xCoxSi2 (0 <= x <= 1) were studied by means of x-ray powder diffraction, magnetization, electrical resistivity and specific heat measurements, at temperatures down to 2 K and in magnetic fields up to 5 T. The experimental data revealed an evolution from strongly anisotropic ferromagnetism with pronounced Kondo effect, observed for the alloys with x < 0.98 and being gradually suppressed with rising Co-content, to spin-glass-like states with dominant spin fluctuations, seen for the sample with x = 0.98. Extrapolation of the value of TC(x) yields a critical concentration xc = 1, at which the magnetic ordering entirely disappears. This finding is in line with preliminary data collected for stoichiometric UCoSi2.Comment: to appear in Phys. Rev.

Magnetic and related properties of ternary TmTX intermetallics

We report on the magnetic and thermal properties of a few TmTX compounds, where T = d-electron metal and X = p-electron element. In all these ternaries but TmRuGe the thulium magnetic moments order antiferro- or ferromagnetically at low temperatures. The specific heat data confirms the magnetic orderings and reveals the influence of crystalline electric field effects

Quasi-two-dimensional Fermi surfaces of the heavy-fermion superconductor Ce2_2PdIn8_8

We report low-temperature de Haas-van Alphen (dHvA) effect measurements in magnetic fields up to 35 T of the heavy-fermion superconductor Ce$_2$PdIn$_8$. The comparison of the experimental results with band-structure calculations implies that the 4$f$ electrons are itinerant rather than localized. The cyclotron masses estimated at high field are only moderately enhanced, 8 and 14 $m_0$, but are substantially larger than the corresponding band masses. The observed angular dependence of the dHvA frequencies suggests quasi-two-dimensional Fermi surfaces in agreement with band-structure calculations. However, the deviation from ideal two dimensionality is larger than in CeCoIn$_5$, with which Ce$_2$PdIn$_8$ bears a lot of similarities. This subtle distinction accounts for the different superconducting critical temperatures of the two compounds.Comment: accepted to Phys. Rev.

Breakdown of the de Gennes scaling in Y1-xDyxNi2B2C

Single crystals of Y1-xDyxΝi2B2C (1 ≤ x≤ 0.7) were examined by X-ray diffraction and stoichiometry was attested by XPS measurements. The superconducting transition temperature T^ and Neel temperature TN were determined by means of magnetisation measurements. A dramatic breakdown of the de Gennes scaling in the Dy-rich compounds was found when < TN