High-magnetic-field and high-pressure effects in monocrystalline URu2Si2

Boer, F.R. de; Franse, J.J.M.; Louis, E. J.; Menovsky, A.A.; Mydosh, J. A.; Palstra, Thomas; Rauchschwalbe, U.; Schlabitz, W.; Steglich, F.; Visser, A. de

doi:10.1016/0378-4363(86)90486-9

Cited by 52 publications

(17 citation statements)

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“…Region (III) may then be the re-entrance of the HO phase with a different nesting wavevector, or an orbital flopped phase. The Fermi surface instabilities produced by the Zeeman effect may also explain the steps observed in the magnetization vs. field [9] as new phases are stabilized. B) Localized f -electrons dominate the low temperature behavior of URu 2 Si 2 and the phase transitions near 40 T are a consequence of crossing singlet f -electron crystal electric field (CEF) levels, as proposed by Santini.…”

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“…external magnetic fields. Pulsed-field measurements of magnetization [9,10,11], resistivity [12,13], Hall effect [13,14], and ultrasonic velocity changes (elastic moduli, c ij ) [15] exhibit a three-step transition between 35 and 40 T for which a satisfactory explanation is still pending.In this Letter we present the first measurements of the temperature -field dependences of the specific heat, magnetocaloric effect and resistivity from 0.5 K to 20 K with fields up to 45 T to attempt to address the outstanding questions discussed above. The measurements indicate four regimes of anomalous behavior as URu 2 Si 2 emerges from its hidden ordered state: (I) The continuous phase transition becomes sharper and symmetric in temperature as magnetic field is increased above 32 T. (II) There is no phase transition to be seen down to 0.5 K at ∼36 T. (III) Between 36 and 39 T a first order-like transition reappears, and (IV) Above 40 T a Schottky-like maximum develops without any sign of a phase transition.…”

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High Magnetic Field Studies of the Hidden Order Transition inURu2Si2

et al. 2002

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We studied in detail the low temperature/high magnetic field phases of URu2Si2 single crystals with specific heat, magnetocaloric effect, and magnetoresistance in magnetic fields up to 45 T. Data obtained down to 0.5 K, and extrapolated to T = 0, show a suppression of the hidden order phase at Ho(0) = 35.9 ± 0.35 T and the appearance of a new phase for magnetic fields in excess of H1(0) = 36.1 ± 0.35 T observed only at temperatures lower than 6 K. In turn, complete suppression of this high field state is attained at a critical magnetic field H2(0) = 39.7 ± 0.35 T. No phase transitions are observed above 40 T. We discuss our results in the context of itinerant vs. localized f -electron behavior and consider the implications for the hidden order phase.During the past few years there has been a true renaissance of interest in the unusual phase transition [1] that occurs in the superconducting heavy fermion system URu 2 Si 2 at T o ≈ 17 K, where all of the thermodynamic and transport properties exhibit a mean-field-like anomaly [2, 3, 4]. These early experimental results led to the conclusion that a magnetic phase transition, possibly of a spin density wave-type, took place. However, when probed with microscopic measurements, e.g., neutron diffraction and muon spin rotation (µSR), only a very tiny magnetic moment of ≈ 0.02 µ B /U was found. Such a small moment could not account for the large changes in behavior at the phase transition and it gradually became apparent that an unconventional type of magnetic order is at play. Indeed, recent neutron diffraction [5], nuclear magnetic resonance [6], and µSR [7] under pressure show the apparent tiny homogeneous moment to be due to a metallurgical minority phase of large moments (≈ 0.3 µ B ), that coexists with a majority (bulk) phase that has no magnetic moments. After more than 15 years of investigation the nature of the bulk phase transition remains unidentified, and the term hidden order (HO) has recently been coined to describe this phenomenon [8]. Besides pressure, yet another external parameter is known to affect the ordered state, i.e. external magnetic fields. Pulsed-field measurements of magnetization [9,10,11], resistivity [12,13], Hall effect [13,14], and ultrasonic velocity changes (elastic moduli, c ij ) [15] exhibit a three-step transition between 35 and 40 T for which a satisfactory explanation is still pending.In this Letter we present the first measurements of the temperature -field dependences of the specific heat, magnetocaloric effect and resistivity from 0.5 K to 20 K with fields up to 45 T to attempt to address the outstanding questions discussed above. The measurements indicate four regimes of anomalous behavior as URu 2 Si 2 emerges from its hidden ordered state: (I) The continuous phase transition becomes sharper and symmetric in temperature as magnetic field is increased above 32 T. (II) There is no phase transition to be seen down to 0.5 K at ∼36 T. (III) Between 36 and 39 T a first order-like transition reappears, and (IV) Above 40 T a Schottky...

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High Magnetic Field Studies of the Hidden Order Transition inURu2Si2

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“…Building on early measurements that showed multiple high field transitions [101,102], it has been determined that there are at least five ordered phases between 30 T and 40 T [103][104][105][106]. Much of the novel physics appears related to a Fermi surface reconstruction near 38 T associated with polarization of the heavy electrons [104,105,107].…”

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“…Figure 21 presents data for UIr as a function of pressure. UIr is an Ising-type ferromagnet with a Curie temperature T C1 ∼ 46 K and the spin easy axis along [101]. The small ratio of the ordered moment (0.5μ B /U ) to the effective moment (2.4μ B /U ) Fig.…”

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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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