Search results for "Heavy fermion superconductor"
showing 8 items of 8 documents
Preparation of superconducting thin films of UNiAl
2005
Abstract Epitaxial thin films of the unconventional heavy fermion superconductor UNi 2 Al 3 we prepared by coevaporation of the elementary components in a molecular beam epitaxy system (MBE). The phase purity and structural quality of the films deposited on (0 1 0)- or (1 1 2)-oriented YAlO 3 substrates were studied by X-ray diffraction and RHEED. The observed R ( T ) behavior is consistent with data obtained from bulk samples and proves the purity of the films. Superconductivity was found with transition temperature T c =0.97 K.
Tunneling junctions of the heavy-fermion superconductor UPd2Al3
1998
Abstract Tunneling spectroscopy on planar Giaever-type junctions is a powerful tool for the investigation of the superconducting state of metals. Since it is possible to prepare high-quality epitaxial thin films of the heavy-fermion compound UPd 2 Al 3 , this method can be used to examine the energy gap of this presumably unconventional superconductor. We prepared cross-junctions consisting of a UPd 2 Al 3 base electrode and a metal counter electrode (Au, Al or Ag). These small area contacts without artificial barriers have only low junction resistances and suffer from irreproducibility. On the other hand, on some of those junctions we observed BCS-like tunneling conductivity. In order to i…
Evidence for Multiband Superconductivity in the Heavy Fermion CompoundUNi2Al3
2004
Epitaxial thin films of the heavy fermion superconductor UNi2Al3 with Tc(max)=0.98 K were investigated. The transition temperature Tc depends on the current direction which can be related to superconducting gaps opening at different temperatures. Also the influence of the magnetic ordering at TN approximately 5 K on R(T) is strongly anisotropic, indicating different coupling between the magnetic moments and itinerant charge carriers on the multisheeted Fermi surface. The upper critical field Hc2(T) suggests an unconventional spin-singlet superconducting state.
Neutron diffraction study of the heavy fermion superconductors UM2Al3(M=Pd, Ni)
1992
An elastic neutron scattering study was performed on the new superconducting heavy fermion systems UPd2Al3 and UNi2Al3. The neutron diffraction patterns reveal unambiguously long range antiferromagnetic order in UPd2Al3 with an ordered magnetic momentμ U = (0.85±0.03)μ B , which coexists with the superconducting state. This is by far the largestμ U value observed for any heavy fermion superconductor. For UNi2Al3, no long-range magnetic order could be observed for temperaturesT≧1.5 K, yielding an upper limit of the ordered moment of 0.2μ B .
Probing the superconducting state of UPd2Al3 thin films by tunneling spectroscopy
1997
Abstract Giaever-type planar cross junctions of thin films of the heavy fermion superconductor UPd2Al3 and counter-electrodes of Au, Ag and Al were prepared. Tunneling barriers consisting of the native oxide layer of UPd2Al3 and artificial barriers of AlOx and UOx were investigated. The junctions without artificial barrier show a lack of reproducebility. On some junctions a BCS-like tunneling conductivity with a ratio of 2Δ 0 /k B T c ⋍ 3.8 was observed. Using oxidized Al deposited at room temperature as a barrier no substantial increase of the junction resistance occured. With Uraniumoxide a much higher resistance was obtained, but an association of the bias dependent junction conductivity…
Preparation of thin films of the heavy fermion superconductor UNi2Al3
2004
Abstract Thin films of the heavy fermion superconductor UNi 2 Al 3 were prepared by coevaporation of the elementary components in an MBE-system. We obtained textured (1 0 0)-oriented films of this hexagonal compound depositing on Al 2 O 3 substrates. Epitaxial growth was observed on (1 1 2)-oriented orthorhombical YAlO 3 substrates. However, due to pronounced strain the UNi 2 Al 3 (1 0 0)-axis is shortened by ≈2%. No superconductivity of the films was observed which can be associated with the high impurity concentration deduced from R ( T ) and XRD investigations.
Anisotropic transport properties ofUNi2Al3thin films
2007
Experimental results on the transport anisotropy in thin films of the heavy fermion superconductor $\mathrm{U}{\mathrm{Ni}}_{2}{\mathrm{Al}}_{3}$ are presented. They show that the eletronic transport in $\mathrm{U}{\mathrm{Ni}}_{2}{\mathrm{Al}}_{3}$ for different directions is strongly dominated by different sheets of the Fermi surface, and that the magnetic moments must be assigned to a cylindrical part around the $c$ axis. Founded on the findings about the Fermi surface, the dependence of the resistive superconducting transition temperature ${T}_{c}$ on the current direction in $\mathrm{U}{\mathrm{Ni}}_{2}{\mathrm{Al}}_{3}$ can be explained as the result of weakly coupled superconducting …
Strong-coupling effects in the heavy-fermion superconductor UPd2Al3
2000
Abstract Recent results of superconducting tunneling spectroscopy on epitaxial thin films of the antiferromagnetic heavy-fermion superconductor UPd 2 Al 3 are presented. Strong-coupling effects in the tunneling density of states are analyzed within the framework of the anisotropic Eliashberg theory for a pair-coupling mechanism based on the exchange of antiferromagnetic spin excitations. The multi-sheeted Fermi surface of UPd 2 Al 3 is taken into account.