We have performed high-pressure, electrical resistivity, and specific heat measurements on CeTe3 single crystals. Two magnetic phases with nonparallel magnetic easy axes were detected in electrical resistivity and specific heat at low temperatures. W
e also observed the emergence of an additional phase at high pressures and low temperatures and a possible structural phase transition detected at room temperature and at 45 kbar, which can possibly be related with the lowering of the charge-density wave transition temperature known for this compound.
A series of high-pressure resistivity measurements on single crystals of TbTe3 reveal a complex phase diagram involving the interplay of superconducting, antiferromagnetic and charge density wave orders. The onset of superconductivity reaches a maximum of ~ 3.5 K (onset) near 75 kbar.
X-ray diffraction, electrical resistivity, magnetization, specific heat, and thermoelectric power measurements are presented for single crystals of the new filled skutterudite compound {CeOsAs}, which reveal phenomena that are associated with f - ele
ctron - conduction electron hybridization. Valence fluctuations or Kondo behavior dominates the physics down to $T$ $sim$ 135 K. The correlated electron behavior is manifested at low temperatures as a hybridization gap insulating state. The small energy gap $Delta$$_1$/k$_B$ $sim$ 73 K, taken from fits to electrical resistivity data, correlates with the evolution of a weakly magnetic or nonmagnetic ground state, which is evident in the magnetization data below a coherence temperature $T$$_{coh}$ $sim$ 45 K. Additionally, the low temperature electronic specific heat coefficient is small, $gamma$ $sim$ 19 mJ/mol K$^2$. Some results for the nonmagnetic analogue compound {LaOsAs} are also presented for comparison purposes.
One of the most notorious non-Fermi liquid properties of both archetypal heavy-fermion systems [1-4] and the high-Tc copper oxide superconductors [5] is an electrical resistivity that evolves linearly with temperature, T. In the heavy-fermion superco
nductor CeCoIn5 [5], this linear behaviour was one of the first indications of the presence of a zero-temperature instability, or quantum critical point. Here, we report the observation of a unique control parameter of T-linear scattering in CeCoIn5, found through systematic chemical substitutions of both magnetic and non-magnetic rare-earth, R, ions into the Ce sub-lattice. We find that the evolution of inelastic scattering in Ce1-xRxCoIn5 is strongly dependent on the f-electron configuration of the R ion, whereas two other key properties -- Cooper-pair breaking and Kondo-lattice coherence -- are not. Thus, T-linear resistivity in CeCoIn5 is intimately related to the nature of incoherent scattering centers in the Kondo lattice, which provides insight into the anomalous scattering rate synonymous with quantum criticality [7].
Magnetization and torque measurements were performed on CeCoIn$_5$ single crystals to study the mixed-state thermodynamics. These measurements allow the determination of both paramagnetic and vortex responses in the mixed-state magnetization. The par
amagnetic magnetization is suppressed in the mixed state with the spin susceptibility increasing with increasing magnetic field. The dependence of spin susceptibility on magnetic field is due to the fact that heavy electrons contribute both to superconductivity and paramagnetism and a large Zeeman effect exists in this system. No anomaly in the vortex response was found within the investigated temperature and field range.
In-plane torque measurements were performed on heavy fermion CeCoIn$_5$ single crystals in the temperature $T$ range 1.8 K $leq T leq 10$ K and applied magnetic field $H$ up to 14 T. The normal-state torque is given by $tau_n propto H^4(1+T/T_K)^{-1}
sin 4phi$. The reversible part of the mixed-state torque, obtained after subtracting the corresponding normal state torque, shows also a four-fold symmetry. In addition, sharp peaks are present in the irreversible torque at angles of $pi/$4, 3$pi$/4, 5$pi$/4, 7$pi$/4, etc. Both the four-fold symmetry in the reversible torque and the sharp peaks in the irreversible torque of the mixed state imply $d_{xy}$ symmetry of the superconducting order parameter. The field and temperature dependences of the reversible mixed-state torque provide further evidence for $d_{xy}$ wave symmetry. The four-fold symmetry in the normal state has a different origin since it has different field and temperature dependences than the one in the mixed state. The possible reasons of the normal state four-fold symmetry are discussed.
Torque and magnetization measurements in magnetic fields $H$ up to 14 T were performed on CeCoIn$_5$ single crystals. The amplitude of the paramagnetic torque shows an $H^{2.3}$ dependence in the mixed state and an $H^{2}$ dependence in the normal st
ate. In addition, the mixed-state magnetizations for both $Hparallel c$ and $Hparallel ab$ axes show anomalous behavior after the subtraction of the corresponding paramagnetic contributions as linear extrapolations of the normal-state magnetization. These experimental results point towards a nonlinear paramagnetic magnetization in the mixed state of CeCoIn$_5$, which is a result of the fact that both orbital and Pauli limiting effects dominate in the mixed state.
Electrical resistivity $rho$, specific heat C, and magnetic susceptibility $chi$ measurements made on the filled skutterudite CeRu_4As_{12} reveal non-Fermi liquid (NFL) T - dependences at low T, i.e., $rho$(T) $sim$ T^{1.4} and weak power law or log
arithmic divergences in C(T)/T and $chi$(T). Measurements also show that the T - dependence of the thermoelectric power S(T) deviates from that seen in other Ce systems. The NFL behavior appears to be associated with fluctuations of the Ce valence between 3^+ and 4^+ rather than a typical Kondo lattice scenario that would be appropriate for an integral Ce valence of 3^+.
