Ferromagnetic instability at the edge of intermediate valence

Abstract

The pressure-temperature phase diagram of the heavy-electron superconductor URu2Si2 has been reinvestigated by ac-susceptibility and elastic neutron-scattering (NS) measurements performed on a small single-crystalline rod (2 mm in diameter, 6 mm in length) in a Cu-Be clamp-type high-pressure cell (P < 1.1 GPa). At ambient pressure, this sample shows the weakest antiferromagnetic (AF) Bragg reflections reported so far, corresponding to the volume-averaged staggered moment of µo∼ 0.011 µB/U. Under applied pressure, the AF scattering intensity exhibits a sharp increase at P ∼ 0.7 GPa at low temperatures. The saturation value of the AF scattering intensity above 0.7 GPa corresponds to µo ∼ 0.41 µB/U, which is in good agreement with that (∼ 0.39µB/U) observed above 1.5 GPa in our previous NS measurements. The superconductivity is dramatically suppressed by the evolution of AF phase, indicating that the superconducting state coexists only with the hidden order phase. The presence of parasitic ferro-and/or antiferromagnetic phases with transition temperatures T

Non-Fermi-liquid behaviour close to the disappearance of ferromagnetism in CePd1−xRhx

“…Figure 1(a) shows zero-field data of C(T )/T for all CePd 1−x Rh x compounds investigated. In the entire temperature range, C(T )/T decreases with increasing x, compatible with the increase of the Kondo temperature with Rh content as deduced from previous studies [7][8][9]. As can be inferred from figure 1(a), the electronic specific-heat coefficient, C(T )/T , of CePd 0.20 Rh 0.80 increases upon cooling, passes a broad maximum at 0.27 K, and saturates at a large value of about 1 J mol −1 K −2 below 0.15 K. Note that previous specific-heat measurements on the same sample, performed above 0.4 K, did not show this anomaly [9].…”

“…Recent studies of physical properties at lower temperatures of the alloys with x 0.60 showed a further decrease of T C with increasing x, down to about 0.25 K for x = 0.80 [8,9]. Specificheat measurements have been performed down to 0.45 K [9]. Overall they show the reduction of the low-temperature specific heat with increasing x, compatible with a strong increase of the Kondo temperature.…”

“…Overall they show the reduction of the low-temperature specific heat with increasing x, compatible with a strong increase of the Kondo temperature. The analysis of the temperature dependence of the 4f contribution to the specific heat C(T )/T suggests NFL behaviour, at least down to 0.45 K. Whereas − log T behaviour is observed below 1 K for x = 0.8 and 0.85, a weak power-law dependence C(T )/T ∼ T −α with α ≈ 0.5 has been found for x = 0.87, 0.90 and 0.95 in the temperature range 0.45 K T 3 K [9].…”

“…Polycrystalline samples of CePd 1−x Rh x with x = 0.80, 0.85, 0.87, 0.90 and 0.95 were prepared as described in [8,9]. Additionally, the non-magnetic reference system LaRh was synthesized.…”

“…In particular, the Curie temperature was found to be suppressed by the Rh doping down to about 3 K in CePd 0.40 Rh 0.60 . Recent studies of physical properties at lower temperatures of the alloys with x 0.60 showed a further decrease of T C with increasing x, down to about 0.25 K for x = 0.80 [8,9]. Specificheat measurements have been performed down to 0.45 K [9].…”