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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: 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: Harry Brian Radousky
Publisher: World Scientific
ISBN: 9789812792655
Category : Science
Languages : en
Pages : 398
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Book Description
Magnetism in Heavy Fermion Systems is a review volume which covers an important subset of topics in the field of heavy fermion and non-Fermi liquid physics. It summarizes much of the experimental information in these areas, and includes an article which discusses theoretical interpretations of the complex magnetic behavior of heavy fermion systems. The topics covered include heavy fermion superconductivity, muon spin relaxation in small-moment heavy fermions, neutron scattering from heavy fermions, random localized magnetism in heavy fermions, and magnetism in Pr-containing cuprates. One feature of the book which should be helpful to graduate students and new workers in the field is the extensive references and a separate list of review articles.
Author: Yoshichika Onuki
Publisher: World Scientific
ISBN: 9813232218
Category : Science
Languages : en
Pages : 336
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Book Description
A large variety of materials prove to be fascinating in solid state and condensed matter physics. New materials create new physics, which is spearheaded by the international experimental expert, Prof Yoshichika Onuki. Among them, the f electrons of rare earth and actinide compounds typically exhibit a variety of characteristic properties, including spin and charge orderings, spin and valence fluctuations, heavy fermions, and anisotropic superconductivity. These are mainly manifestations of better competitive phenomena between the RKKY interaction and the Kondo effect. The present text is written so as to understand these phenomena and the research they prompt. For example, superconductivity was once regarded as one of the more well-understood many-body problems. However, it is, in fact, still an exciting phenomenon in new materials. Additionally, magnetism and superconductivity interplay strongly in heavy fermion superconductors. The understanding of anisotropic superconductivity and magnetism is a challenging problem in solid state and condensed matter physics. This book will tackle all these topics and more.
Author: Neil Adam Frederick
Publisher:
ISBN:
Category :
Languages : en
Pages : 260
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Book Description
Author: M. Tachiki
Publisher: Elsevier
ISBN: 1483275175
Category : Science
Languages : en
Pages : 561
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Book Description
Superconductivity in Highly Correlated Fermion Systems documents the proceedings of the Yamada Conference XVIII on Superconductivity in Highly Correlated Fermion Systems held in Sendai, Japan, from August 31 to September 3, 1987. This book compiles selected papers on the experimental and theoretical advances in the study of superconductivity. The topics include the superconductivity and magnetism in heavy-electron materials, magneto-resistance of heavy-fermion compounds, and magnetic fluctuations and order in exotic superconductors. The fabrication and properties of thin superconducting oxide films, bipolaron models of superconductors, superconducting properties of superlattices, and flux quantization on quasi-crystalline networks are also covered. This publication is recommended for physicists and students researching on the superconductivity in highly correlated fermion systems.
Author: L C Gupta
Publisher: World Scientific
ISBN: 9814505129
Category : Science
Languages : en
Pages : 684
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Book Description
Contents:The First Five Years of High-Tc Superconductivity (K A Müller)Different Factors which Govern the Optimisation of High-Tc Superconductive Cuprates Involving Bi-, Tl or Pb (B Raveau, M Hervieu, C Michel, J Provost, A Maignan, C Simon & D Groult)Superconductivity in Cuprates and Other Oxides (H R Ott)Organic Superconductors with Tc Higher than 10K (T Ishiguro & Y Nogami)Fundamentals of RVB Theory and Some Applications to High Temperature Superconductors (G Baskaran)Anyons and Superconductivity (S Das Sarma)Mott Transition in the Hubbard Model (B S Shastry)Superconducting Pairing in Layered Superconductors (S S Jha)Breaking the Log-Jam in Many-Body Physics: Fermi Surfaces Without Fermi Liquids (P W Anderson)Superconductivity in High Magnetic Fields from a Microscopic Theory (A K Rajagopal)Nonequilibrium Superconductivity (R Tidecks)Neutron Scattering Study of the High-Tc Superconducting System YBa2Cu3O6+x (J Rossat-Mignod et al.)Crystal-Field Excitations in High-Tc Superconducting Materials (A Furrer)Superconducting Granular Films (S-I Kobayashi)Transport Properties in the Mixed State of High Temperature Superconductors (A Freimuth)Physics of Josephson Effect and Recent Advances (A Barone & S Pagano)Tunneling Spectroscopy of Copper Oxide Superconductors (T Ekino & J Akimitsu)Superconductivity and Magnetism in Heavy-Fermion Compounds (F Steglich, U Ahlheim, C D Bredl, C Geibel, M Lang, A Loidl & G Sparn)Nuclear Magnetic Resonance Studies in Highly Correlated Systems: Heavy Fermion and High-Tc Superconductors (K Asayama)Pulsed Laser and Cylindrical Magnetron Sputter Deposition of Epitaxial Metal Oxide Thin Films (T Venkatesan et al.) Readership: Physicists, chemists and engineers. keywords:
Author: William M. Yuhasz
Publisher:
ISBN:
Category :
Languages : en
Pages : 146
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Book Description
In the search for new and interesting strongly correlated electron phenomena, a detailed study has been underway of the rare earth-based filled skutterudite compounds. This work has been driven by the rich variety of strongly correlated electron phenomena exhibited by the filled skutterudites such as metal insulator transitions, heavy fermion behavior, quadrupole ordering, non-Fermi liquid behavior, and heavy fermion superconductivity. The filled skutterudite compounds have the chemical formula MT4X12 where M = alkali metal, alkaline-earth, lanthanide, or actinide; T = Fe, Ru, or Os; and X = P, As, or Sb. To improve the general understanding of these systems and to look for other strongly correlated electron behavior, single crystals of Pr0.87Fe4Sb12, PrOs4As12, \PrOs4P12, SmOs4Sb12, and NdOs4Sb12 were grown and characterized with X-ray diffraction, magnetization, electrical resistivity and specific heat measurements. Measurements of the filled skutterudite compound Pr0.87Fe4Sb12 reveal long rang magnetic ordering below 4.1 K with indications of ferrimagnetic ordering. Features in the magnetization of the filled skutterudite PrOs4As12 are consistent with antiferromagnetic ordering below 2.3 K. The specific heat, electrical resistivity, and magnetization measurements on PrOs4As12 also show features consistent with at least 2 to 3 ordered phases. Strong crystalline electric field effects were observed in PrOs4P12 and SmOs4Sb12, with both systems exhibiting Schottky anomalies in specific heat measurements. Magnetic ordering was observed in SmOs4Sb12 below 2.6 K with a ferromagnetic component as indicated by hysteresis in the magnetization as a function of field at 2 K. Magnetic ordering was also observed in the filled skutterudite compound NdOs4Sb12 below 0.9 K. Analysis of the specific heat measurements on Pr0.87Fe4Sb12, PrOs4As12, SmOs4Sb12, and NdOs4Sb12 reveal an enhanced electron effective mass, with SmOs4Sb12 showing the largest enhancement.
Author: A. D. Christianson
Publisher:
ISBN:
Category : Fermions
Languages : en
Pages : 266
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Author: Dom Lal Kunwar
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The heavy fermions (HF) are strongly correlated electron systems consisting of intermetallic compounds of lanthanides and actinides ions with f -electrons unfilled shells. These systems are very rich in physics and the interplay between competing interactions results in various interesting physical phenomena such as heavy fermion behavior, unconventional superconductivity, non-Fermi-liquid behavior, coexistence of superconductivity and magnetism, and quantum criticality. The origin of such phenomena comes from the interaction of itinerant conduction states with the partially filled 4f - or 5f -electron states of rare earth elements. The study of such important physical phenomena can be possible by tuning the system using nonthermal control parameters, such as chemical composition, magnetic field, and applied pressure. So, studying the chemical pressure effect on heavy fermion systems with or without magnetic field is an intriguing idea to construct various phase diagrams and study their phase transitions. We performed heat capacity (HC), magnetoresistance (MR), and resistivity measurements on the Ce-based 115 and U-based 122 heavy fermion materials at low temperatures. We studied the nature of the quantum critical point, second-order phase transition, and the possible interplay between superconductivity and magnetism. First, we were motivated by the possibility of observing the coexistence of magnetism and unconventional superconductivity in the heavy fermion Ce1-xSmxCoIn5 alloys. We performed specific heat, MR, and resistivity measurements in different magnetic fields. We investigated how the samarium substitution on the cerium site affects the magnetic-field-tuned quantum criticality of stoichiometric CeCoIn5. We have observed Fermi-liquid to non-Fermi-liquid crossovers in the temperature dependence of the electronic specific heat and resistivity at higher external magnetic fields. We obtained the magnetic-field-induced quantum critical point (HQCP) by extrapolating the crossover temperature to zero temperature. Furthermore, we performed a scaling analysis of the electronic specific heat and confirmed the existence of the QCP. According to our findings, the magnitude of (HQCP) decreases as the samarium content rises and ultimately becomes zero. The electronic specific heat and resistivity data reveal a zero-field QCP for xcr = 0.15, which falls inside the antiferromagnetic and superconducting coexistence region. Next, we performed measurements of the heat capacity as a function of temperature in a single crystals URu2-xOsxSi2. Our experimental results show that the critical temperature of the second-order phase transition increases while the value of the Sommerfeld coefficient in the ordered state decreases with an increase in osmium concentration. We also observed the increase in the magnitude of the heat capacity at the critical temperature and a broadening of the critical fluctuations region with an increase in Os concentration. We analyze the experimental data using the Haule- Kotliar model, which identifies the 'hidden order' transition in the parent material URu2Si2 as a transition to a state with nonzero hexadecapolar moment. We showed that our experimental results are consistent with this model. In conclusion, we studied the interplay between superconductivity and magnetism in Ce based 115 and U based 122 single crystal alloys using heat capacity, magnetoresistivity, and resistivity measurements in both cryogenic systems including He-4 and He-3. The understating of various phenomena in these heavy fermions could be helpful in developing higher transition temperature superconductors, energy storage devices, quantum computers, and memory devices in the future.
