Neutron diffraction study of the heavy fermion superconductors UM2Al3(M=Pd, Ni)

Krimmel, A.; Fischer, Peter; Roessli, B.; Maletta, H.; Geibel, C.; Schank, C.; Grauel, A.; Loidl, A.; Steglich, F.

doi:10.1007/bf01313821

Cited by 235 publications

(92 citation statements)

References 6 publications

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“…Here, both the structure of the basal plane of UPd 2 Al 3 with the assignment of the a and b axes ( figure 1(a)) as well as the unit cell of UPd 2 Al 3 in the hexagonal supercell ( figure 1(b)) are shown. The arrows on the U atoms illustrate the structure of the magnetic ordering in zero magnetic field with a wave vector q = ( 1 2 00) [11]. The torque experiments were performed in Grenoble and in Leiden.…”

Section: Experimental Techniquesmentioning

confidence: 99%

The magnetic torque of the heavy-fermion system

Süllow

Janossy

Vliet

et al. 1996

J. Phys.: Condens. Matter

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The magnetic torque of the heavy-fermion Upd2Ga3Sullow, S.; Janossy, B.; van Vliet, G.E.L.; Nieuwenhuys, G.J.; Menovsky, A.A.; Mydosh, J.A. Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Abstract. The basal-plane anisotropy of the antiferromagnetic phase of the hexagonal heavy-fermion superconductor UPd 2 Al 3 has been studied via the magnetic torque. Torque measurements were performed as functions of magnetic field and angle, with the field rotated in the a-b-plane, at temperatures between 4.2 and 30 K and in fields of up to 20 T. We interpret our results within a mean-field model and derive expressions for the basal-plane anisotropy energy. Further, we studied the anisotropy and temperature dependence of the metamagnetic transition of UPd 2 Al 3 at 18 T and we discuss its nature.

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Section: Experimental Techniquesmentioning

confidence: 99%

The magnetic torque of the heavy-fermion system

Süllow

Janossy

Vliet

et al. 1996

J. Phys.: Condens. Matter

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“…The NFL behavior in these three systems, U 1−x M x Pd 2 Al 3 (M = Th, Y, La), apparently originates from two different mechanisms: an unconventional Kondo effect (M = Th) and fluctuations of an order parameter in the vicinity of an SG QCP (M = Y, La). The parent compound UPd 2 Al 3 has a moderately large electron effective mass m * ≈ 50m e , inferred from an electronic specific heat coefficient γ ≈ 140 mJ/mol K 2 [66], and exhibits the coexistence of AFM order with a Néel temperature T N = 14.6 K and superconductivity with T c ∼ 2 K. The AFM structure consists of an AFM stacking along the c-axis of FM planes with relatively large ordered moments of ∼0.85 μ B lying in the hexagonal basal plane [67]. In the following discussion, we briefly describe the T -x phase diagrams and NFL behavior observed in the Th, Y, and La substituted UPd 2 Al 3 based systems.…”

Section: Y 1−x U X Pdmentioning

confidence: 99%

Non-Fermi Liquid Regimes and Superconductivity in the Low Temperature Phase Diagrams of Strongly Correlated d- and f-Electron Materials

et al. 2010

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Standard models for simple metals and insulators often fail for systems based on elements with unstable d-or f -electron shells, where strong electronic correlations can generate new and unexpected states of matter. Such a scenario can often be induced when a magnetic phase transition is tuned to absolute zero temperature by an external control parameter such as chemical composition, pressure or magnetic field. At the resulting quantum critical point (QCP), emergent phenomena, such as unconventional superconductivity and novel magnetic phases are frequently observed. The temperature and energy dependences of the physical properties are also found to deviate from expectations for a simple Fermi liquid. This "non-Fermi-liquid" (NFL) behavior is commonly manifested as weak power laws and logarithmic divergences in the physical properties at low temperatures and is often found in a V-shaped region near a QCP, which has become the "classic" QCP phase diagram. However, there is also a growing number of materials where the NFL behavior either occurs far away from the QCP, within an ordered phase, or may not be associated with any putative QCP. Thus, after nearly 20 years of research, it remains unknown whether NFL physics is universal, or if a multitude of unique subclasses exist. In this article, we review research that has primarily been carried out in our laboratory on systems that exhibit NFL behavior that does not conform to the "classic" QCP scenario.

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“…UPd 2 Al 3 has a hexagonal PrNi 2 Al 3 -type structure with the space group P 6/mmm and exhibits antiferromagnetic (AFM) order at the Néel temperature T N = 14.5 K with a commensurate wave vector Q AF = (0, 0, 0.5) and well-localized magnetic moment of ∼ 0.85 µ B /U. 3,4) After the AFM transition occurs, superconductivity is observed below the SC transition temperature T c = 2 K. 5) NMR and µSR measurements provide evidence for a spin-singlet Cooper pairing from the clear decrease in the Knight shift below T c . 6, 7) Large specific-heat jump at T c 5) indicates that heavy electrons form Cooper pairs; thus, the orbital pair-breaking field becomes large.…”

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Spatially Inhomogeneous Superconducting State near H_c2 in UPd₂Al₃

et al. 2018

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We have performed 27 Al-NMR measurements on single-crystalline UPd2Al3 with the field parallel to the c axis to investigate the superconducting (SC) properties near the upper critical field of superconductivity Hc2. The broadening of the NMR linewidth below 14 K indicates the appearance of the internal field at the Al site, which originates from the antiferromagnetically ordered moments of U 5f electrons. In the SC state well below µ0Hc2 = 3.4 T, the broadening of the NMR linewidth due to the SC diamagnetism and a decrease in the Knight shift are observed, which are well-understood by the framework of spin-singlet superconductivity. In contrast, the Knight shift does not change below Tc(H), and the NMR spectrum is broadened symmetrically in the SC state in the field range of 3 T < µ0H < µ0Hc2. The unusual NMR spectrum near Hc2 suggests that a spatially inhomogeneous SC state such as the Fulde-Ferrell-LarkinOvchinnikov (FFLO) state would be realized.Superconductivity in the presence of magnetic fields close to the upper critical field (H c2 ) is the critical state where the intriguing physical phenomena are anticipated. In general, there are two well-known pair-breaking mechanisms in a type-II superconductor under magnetic fields. One is the orbital pair-breaking effect related to the emergence of Abrikosov vortices, and the superconductivity is destroyed at the vortex cores. The other is the Pauli pair-breaking effect, which originates from the Zeeman splitting of spin-singlet Cooper pairs. When the Zeeman-splitting energy is as large as the condensation energy of superconductivity, the superconductivity becomes unstable and transitions to the normal state. The strong contribution of the Pauli pair-breaking effect leads to many interesting issues, such as the realization of the spatially modulated superconducting (SC) state, which is called the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. 1, 2) For the realization of the FFLO state, a very clean system is necessary; thus, not many compounds have been pointed out as candidates for the FFLO state.UPd 2 Al 3 is one such candidate for the FFLO state. UPd 2 Al 3 has a hexagonal PrNi 2 Al 3 -type structure with the space group P 6/mmm and exhibits antiferromagnetic (AFM) order at the Néel temperature T N = 14.5 K with a commensurate wave vector Q AF = (0, 0, 0.5) and well-localized magnetic moment of ∼ 0.85 µ B /U. 3, 4) After the AFM transition occurs, superconductivity is observed below the SC transition temperature T c = 2 K. 5) NMR and µSR measurements provide evidence for a spin-singlet Cooper pairing from the clear decrease in the Knight shift below T c . 6, 7) Large specific-heat jump at T c 5) indicates that heavy electrons form Cooper pairs; thus, the orbital pair-breaking field becomes large. As a result, the suppression of superconductivity by the Pauli pair-breaking effect is expected. Moreover, a pronounced hysteresis behavior has been observed in a narrow field range below H c2 , H * < H < H c2 , with several different experiments, such as magnetizatio...

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Neutron diffraction study of the heavy fermion superconductors UM2Al3(M=Pd, Ni)

Cited by 235 publications

References 6 publications

The magnetic torque of the heavy-fermion system

The magnetic torque of the heavy-fermion system

Non-Fermi Liquid Regimes and Superconductivity in the Low Temperature Phase Diagrams of Strongly Correlated d- and f-Electron Materials

Spatially Inhomogeneous Superconducting State near H_c2 in UPd₂Al₃

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Neutron diffraction study of the heavy fermion superconductors UM2Al3(M=Pd, Ni)

Cited by 235 publications

References 6 publications

The magnetic torque of the heavy-fermion system

The magnetic torque of the heavy-fermion system

Non-Fermi Liquid Regimes and Superconductivity in the Low Temperature Phase Diagrams of Strongly Correlated d- and f-Electron Materials

Spatially Inhomogeneous Superconducting State near Hc2 in UPd2Al3

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Spatially Inhomogeneous Superconducting State near H_c2 in UPd₂Al₃