Superconductivity, Heavy Fermion Behavior, and Crystalline Electric Field Effects in the Filled Skutterudite Series Pr(Os̳1̳-x̳RUx̳)̳4Sb̳1̳2 PDF Download
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Author: Neil Adam Frederick
Publisher:
ISBN:
Category :
Languages : en
Pages : 260
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Book Description
Author: Neil Adam Frederick
Publisher:
ISBN:
Category :
Languages : en
Pages : 260
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Book Description
Author: Ram Bahadur Adhikari
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Strongly correlated electron systems constitute a rich reservoir for interesting physical phenomena. The competition and interplay between the localized magnetic moments in partially filled d or f electron systems and the itinerant conduction electrons states lead to novel phenomena such as complex magnetic properties, unconventional superconductivity, non-Fermi-liquid behavior, and the coexistence of superconductivity and magnetism. Such intriguing physical phenomena can be achieved by tuning the system with a control parameter, such as chemical composition, applied pressure, and magnetic field. It is interesting to study the chemical substitution effects on the correlated f electron system along with magnetic field to explore their complex phase diagram. This dissertation work focuses on experimental studies of the Ce and Eu substituted filled skutterudite system PrPt4Ge12 over a wide range of doping, magnetic field, and temperature using heat capacity measurements. The first study will focus on the specific heat and electrical resistivity measurements performed on the Pr[subscript 1-x]Ce[subscript x]Pt4Ge12 crystals. We have found that Ce monotonically suppresses the superconducting transition temperature T[subscript c] and a small Ce concentration of x = 0.14 brings the T[subscript c] to as low as 0.6 K. We further have demonstrate that small Ce substitution does not affect the multiband nature of superconductivity seen previously in the parent compound PrPt4Ge12. On the other hand, our data provide evidence that one of the two gaps is nodal in the parent compound and that Ce substitution gradually suppresses the value of the nodal gap. To understand the possible interplay between superconductivity and magnetism, we study the same parent system PrPt4Ge12, this time substituting Pr with europium. The compound so formed is Pr[subscript 1-x]Eu[subscript x]Pt4Ge12 whose end members are superconductor (x = 0) and antiferromagnetic (x = 1) at lower temperatures, so that there is the possibility of interaction between superconductivity and magnetism in the intermediate doping range. The increase of Eu concentration leads to a suppression of the superconducting transition temperature as in the case of cerium substitution. There is a low temperature heat capacity anomaly present over the whole doping range. Our analysis of the heat capacity data shows that in alloys with x = 0.5 the Schottky peaks in the heat capacity in the superconducting state appear to be due to Zeeman splitting by an internal magnetic field. Our theoretical analysis suggests that this internal magnetic field is a result of short-range antiferromagnetic correlations between the europium ions. We further investigated the effect of Eu substitution on the Pr site through heat capacity measurements on the same system in an applied magnetic field. The low temperature heat capacity peaks seen in the samples with x
Author: Ctirad Uher
Publisher: CRC Press
ISBN: 1000513807
Category : Science
Languages : en
Pages : 418
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Book Description
Superconductivity and Magnetism in Skutterudites discusses superconducting and magnetic properties of a class of materials called skutterudites. With a brief introduction of the fundamental structural features of skutterudites, the book then provides a detailed assessment of the superconducting and magnetic properties, focusing particularly on the rare earth-filled skutterudites where a plethora of fascinating properties and ground states is realized due to interactions of the filler species with the framework ions. Such interactions underpin the exciting forms of superconductivity and magnetism, most notably realized in the exotic heavy fermion superconductor of composition PrOs4Sb12. The two main topics of superconductivity and magnetism are provided with a concise introduction of superconducting and magnetic properties so that a reader can appreciate and understand the main arguments in the text. This book would appeal to graduate students, postdoctoral students, and anyone interested in superconducting and magnetic properties of a large family of minerals called skutterudites. Key Features: • Gives a thorough account of the superconducting and magnetic properties of skutterudites. • Each topic is accompanied by introductory sections to assist in the understanding of the text. • Supported by numerous figures and all key references.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 6
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Book Description
The main goal of this program was to explore the possibility of novel states and behaviors in Pr-based system exhibiting quantum critical behavior, PrOs4Sb12. Upon small changes of external parameter, such as magnetic field, physical properties of PrOs4Sb12 are drastically altered from those corresponding to a superconductor, to heavy fermion, to field-induced ordered phase with primary quadrupolar order parameter. All these states are highly unconventional and not understood in terms of current theories thus offer an opportunity to expand our knowledge and understanding of condensed matter. At the same time, these novel states and behaviors are subjects to intense international controversies. In particular, two superconducting phases with different transition temperatures were observed in some samples and not observed in others leading to speculations that sample defects might be partially responsible for these exotic behaviors. This work clearly established that crystal disorder is important consideration, but contrary to current consensus this disorder suppresses exotic behavior. Superconducting properties imply unconventional inhomogeneous state that emerges from unconventional homogeneous normal state. Comprehensive structural investigations demonstrated that upper superconducting transition is intrinsic, bulk, and unconventional. The high quality of in-house synthesized single crystals was indirectly confirmed by de Haas-van Alphen quantum oscillation measurements. These measurements, for the first time ever reported, spanned several different phases, offering unprecedented possibility of studying quantum oscillations across phase boundaries.
