Dexuan Huo

RKKY Interaction and Kondo Effect in (Ce, La)PdSn

Measurements of the magnetic susceptibility (2–300 K), electrical resistivity (70 mK–300 K), specific heat (70 mK–150 K) and thermoelectric power (0.3–300 K) have been carried out on Ce x La 1- x PdSn. For all these quantities, the crystalline electric field (CEF) effect on Ce 3+ state was observed: the CEF splitting scheme does not change much for x ≥0.3. The Neel temperature decreases monotonically with decreasing Ce concentration, and the long-range antiferromagnetic order disappears for x around 0.1. The thermoelectric power of Ce x La 1- x PdSn shows complicated structures at low temperatures. These results were discussed from the viewpoint of coexistence and competition between the RKKY interaction and the Kondo effect.

Thermoelectric Power of CePt1-xNix

The thermoelectric power, S , of samples of CePt 1- x Ni x has been measured as a function of temperature, T , from 2 K to room temperature. The present samples are the ternary alloy system of CeNi [an intermediate valence (IV) compound] and of CePt, one of the few compounds classified as a Kondo-ferromagnet. The S ( T ) curves present a continuous evolution through the compositions studied. For the richer Ni compounds x >0.9 we recover the characteristic features of the IV compounds while for the rest of the ordered compounds, S ( T ) presents a complex structure reflecting the competition of RKKY and Kondo interactions. The initial slopes, α, of the S ( T ), estimated at T =0, have the same variation as the electronic specific-heat coefficient, γ, with the Ni concentration, x , presenting a broad maximum at around x =0.85, near to the concentration of disappearance of the ferromagnetic order.

Tuning of Magnetic Properties and Kondo Effect by Cu Concentration in Ce(Pd1-xCux)2Al3

The electrical resistivity, magnetic susceptibility and specific heat measurements were performed on Ce(Pd 1- x Cu x ) 2 Al 3 ( x =0.0–0.7) system to investigate the effects induced by Cu substitution in the heavy fermion compound CePd 2 Al 3 . A dramatic evolution of the magnetic properties was observed with the substitution of Pd by Cu: (1) a small amount of Cu ( x < 0.1) in CePd 2 Al 3 leads to a rapid decrease of the antiferromagnetic transition temperature T N ; (2) passing through a crossover region without a long-range magnetic order, a ferromagnetic-like state, which reveals an enhanced magnetic susceptibility and a distinct peak in the specific heat curve at low temperatures, occurs around x =0.1–0.4; (3) by furthering the substitution through a second crossover region, however, the antiferromagnetic ordering is recovered close to x =0.5–0.7. A decrease tendency of the Kondo temperature T K with increasing x is derived from the analysis on the specific heat results. It is suggested that the chang...

Transport properties of Ce(NixPd1−x)2Si2

Abstract The electrical resistivity and the thermoelectric power of Ce(Ni x Pd 1− x ) 2 Si 2 have been investigated. The chemical pressure effect caused by substitution of Pd with Ni on the electrical resistivity and the thermoelectric power was found to be very similar to the effect of hydrostatic pressure. The ground state of Ce(Ni x Pd 1− x ) 2 Si 2 changes gradually from an antiferromagnetic Kondo state ( x x >0.3) with increasing x . The non-magnetic heavy fermion state seems to be realized at x ≈0.2–0.3.

Magnetic, Thermal and Transport Properties of Ce(Ni1-xCux)2Al3: The Dominant Role of Electronic Change

The Ni sites of an intermediate-valence compound CeNi 2 Al 3 can be partially substituted with Cu atoms up to 40%. Both the unit-cell volume and the number of conduction electrons increase with the...

Heavy fermion behavior in Ce(NixPd1−x)2Si2

Measurements of the magnetic susceptibility χ, specific heat C, and thermoelectric power S were carried out for the solid solution Ce(NixPd1−x)2Si2 (0⩽x⩽1). With increasing x, the ground state changes from an antiferromagnetic Kondo state (x 0.3). The heavy fermion state was found to evolve at the crossover concentration at x=0.2, where the long-range magnetic order seems to disappear.

Thermoelectric power of the superconducting pyrochlore Cd2Re2O7

We report the thermoelectric power (S) of the recently discovered superconducting pyrochlore Cd2Re2O7 with Tc = 1.4?K. In the normal state, this compound shows a continuous structural phase transition at T* = 200?K. S is negative from room temperature down to 1.4?K. Above T*, S shows small absolute values and approximatively linear dependence on temperature. S(295?K) = -2.2??V?K-1. The absolute value of S increases rapidly below T*. A kink and a minimum were observed round 125 and 60?K, respectively. S(60?K) = -8.2??V?K-1. In the low-temperature range 1.4?K<T<20?K, another linear portion was observed. As regards the T2-dependent electrical resistivity in this temperature range, a Fermi liquid ground state is suggested for this compound. No change of S in a magnetic field up to 2?T was observed at 77 and 295?K.

Antiferromagnetism in Ce(Ni1−xPdx)2Ge2 single crystals near magnetic instability

Abstract We have measured specific heat and electrical resistivity of Ce(Ni1−xPdx)2Ge2 (x=0.09 and 0.12) single crystals with antiferromagnetic ground state. For x∼0.12 crystal, there is no obvious rise in the electrical resistivity around the Neel temperature TN. This antiferromagnetic ordering might be understood as the itinerant antiferromagnetism of heavy-quasiparticles without the gapping behavior.

The Sign of Magneto-Thermoelectric Power of Magnetic Granular Alloys

The thermoelectric power S and magneto-thermoelectric power δ S = S ( H )- S (0) were measured for Fe–Cu and Fe–Ag granular alloys. The sign of both S and δ S of the measured samples was confirmed to be negative, similar to that of all the other granular alloys, contrary to the theories proposed hitherto. We point out the importance of the Kondo effect of the magnetic impurities between the magnetic and non-magnetic clusters, and we show we can understand successfully the sign of both S and δ S from this standpoint.

Thermoelectric power of CePd1-xNixAl single crystals

Abstract The thermoelectric power S of CePd1−xNixAl (x=0,0.1,0.2,0.4,1) single crystals was investigated. Ss along the a- and c-axis of CePdAl, namely Sa and Sc, show a positive peak around 180 K and a negative peak at 30 K . In addition, Sa shows the second maximum around 5 K . Correspondingly, Sc shows an upward curvature in the same temperature range. For x=0.1, S along the two directions shows double peak structure with positive value in the temperature range of the measurement. For x=0.2, S shows the behavior of nonmagnetic heavy fermion (HF)systems. For x⩾0.4, a broad peak of S was observed along both directions. CePd1−xNixAl with x⩾0.4 belongs to the valence fluctuation regime.