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Title: Doping experiments in heavy fermion superconductors

Abstract

Experimental results are presented on the doping effects both in the normal state and the superconducting state of the heavy fermion superconductors UBe[sub 13], CeCu[sub 2]Si[sub 2], and UPt[sub 3]. The objective has been to understand the origin of heavy fermion nature and the unusual superconductivity in these materials. In the normal state, U 5f-electron hybridization with Be s-electrons controls the specific heat [gamma] and m* in the U-dilute limit of x > 0.15 in U[sub 1[minus]x]M[sub x]Be[sub 13]. For a[sub 0](U[sub 1[minus]x]M[sub x]Be[sub 13]) [le] (UBe[sub 13]) in lattice parameter, [gamma] per U-mole is due to single ion effects. The large low-temperature magnetic susceptibility in UBe[sub 13] is entirely attributable to single-ion effects, contrary to previous assumptions. A huge low-temperature [chi] per Ce-mole and M vs. H saturation are found in Ce[sub 1[minus]x]Th[sub x]Cu[sub 2]Si[sub 2] (x > 0.75). It is found that Ti in UPt[sub 3] suppresses magnetism in contrast to the other isoelectronic dopants (Hf, Zr) and suppresses spin fluctuation faster than Hf and Zr possibly due to the stronger hybridization for 3d- and 4s-orbitals of Ti with the 5f-orbital of U. In the superconducting state, the author reports specific heat and [Tc] on the highest puritymore » UBe[sub 13] to date. The high-purity annealed samples show larger and sharper transition temperatures of U[sub 0.97]Tho[sub 0.03]Be[sub 13] are parallel within the error, and these results (H[prime][sub c2] ([Tc]) [approx] [minus]45 [+-] 3 T/K, H[prime][sub c2] ([Tc]) = dH[sub c2](T)/dT at [Tc]) are almost identical with the H[prime][sub c2]([Tc]) value of pure UBe[sub 13]. The equality of H[prime][sub c2]([Tc][sub 1]), H[prime][sub c2]([Tc][sub 2]) for U[sub 0.97]Th[sub 0.03]Be[sub 13], and H[prime][sub c2]([Tc]) for pure UBe[sub 13] is difficult to explain on the basis of current theories that consider the lower transition as a magnetic superconducting state.« less

Authors:
Publication Date:
Research Org.:
Florida Univ., Gainesville, FL (United States)
OSTI Identifier:
5431331
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph.D.)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; SUPERCONDUCTORS; CRYSTAL DOPING; FABRICATION; ALUMINIUM; BERYLLIUM ALLOYS; CESIUM ALLOYS; COPPER SILICATES; CRYSTAL LATTICES; EXPERIMENTAL DATA; F STATES; FERMIONS; GALLIUM; HAFNIUM; HYBRIDIZATION; ISOELECTRONIC ATOMS; LATTICE PARAMETERS; MAGNETIC SUSCEPTIBILITY; METALLURGICAL EFFECTS; NICKEL; PLATINUM ALLOYS; S STATES; SPECIFIC HEAT; TITANIUM; TRANSITION TEMPERATURE; URANIUM ALLOYS; ZIRCONIUM; ACTINIDE ALLOYS; ALLOYS; ATOMS; COPPER COMPOUNDS; CRYSTAL STRUCTURE; DATA; ELEMENTS; ENERGY LEVELS; INFORMATION; MAGNETIC PROPERTIES; METALS; NUMERICAL DATA; OXYGEN COMPOUNDS; PHYSICAL PROPERTIES; PLATINUM METAL ALLOYS; SILICATES; SILICON COMPOUNDS; THERMODYNAMIC PROPERTIES; TRANSITION ELEMENT COMPOUNDS; TRANSITION ELEMENTS; 360107* - Metals & Alloys- Superconducting Properties- (1992-); 360101 - Metals & Alloys- Preparation & Fabrication

Citation Formats

Kim, J. Doping experiments in heavy fermion superconductors. United States: N. p., 1992. Web.
Kim, J. Doping experiments in heavy fermion superconductors. United States.
Kim, J. Wed . "Doping experiments in heavy fermion superconductors". United States.
@article{osti_5431331,
title = {Doping experiments in heavy fermion superconductors},
author = {Kim, J},
abstractNote = {Experimental results are presented on the doping effects both in the normal state and the superconducting state of the heavy fermion superconductors UBe[sub 13], CeCu[sub 2]Si[sub 2], and UPt[sub 3]. The objective has been to understand the origin of heavy fermion nature and the unusual superconductivity in these materials. In the normal state, U 5f-electron hybridization with Be s-electrons controls the specific heat [gamma] and m* in the U-dilute limit of x > 0.15 in U[sub 1[minus]x]M[sub x]Be[sub 13]. For a[sub 0](U[sub 1[minus]x]M[sub x]Be[sub 13]) [le] (UBe[sub 13]) in lattice parameter, [gamma] per U-mole is due to single ion effects. The large low-temperature magnetic susceptibility in UBe[sub 13] is entirely attributable to single-ion effects, contrary to previous assumptions. A huge low-temperature [chi] per Ce-mole and M vs. H saturation are found in Ce[sub 1[minus]x]Th[sub x]Cu[sub 2]Si[sub 2] (x > 0.75). It is found that Ti in UPt[sub 3] suppresses magnetism in contrast to the other isoelectronic dopants (Hf, Zr) and suppresses spin fluctuation faster than Hf and Zr possibly due to the stronger hybridization for 3d- and 4s-orbitals of Ti with the 5f-orbital of U. In the superconducting state, the author reports specific heat and [Tc] on the highest purity UBe[sub 13] to date. The high-purity annealed samples show larger and sharper transition temperatures of U[sub 0.97]Tho[sub 0.03]Be[sub 13] are parallel within the error, and these results (H[prime][sub c2] ([Tc]) [approx] [minus]45 [+-] 3 T/K, H[prime][sub c2] ([Tc]) = dH[sub c2](T)/dT at [Tc]) are almost identical with the H[prime][sub c2]([Tc]) value of pure UBe[sub 13]. The equality of H[prime][sub c2]([Tc][sub 1]), H[prime][sub c2]([Tc][sub 2]) for U[sub 0.97]Th[sub 0.03]Be[sub 13], and H[prime][sub c2]([Tc]) for pure UBe[sub 13] is difficult to explain on the basis of current theories that consider the lower transition as a magnetic superconducting state.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1992},
month = {1}
}

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