The goal of our work is to gain more insight into the vortex dynamics in YBa2Cu3O7-delta single crystals with point defects induced by 9 MeV proton irradiation. In order to accomplish a comparative study, different crystals and... more
The goal of our work is to gain more insight into the vortex dynamics in YBa2Cu3O7-delta single crystals with point defects induced by 9 MeV proton irradiation. In order to accomplish a comparative study, different crystals and irradiation doses were used. The results were correlated using both electrical transport and ac specific heat measurements. Special attention was given to investigating the nature of the vortex state below the lower critical point of the first order vortex melting transition. This work was supported by the National Science Foundation through Grant DMR-0072880 and the U. S. Department of Energy, Basic Energy Sciences contract W-31-109-ENG-38.
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Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Thermodynamics, Superconductivity, and 11 moreMagnetic field, Phase transition, First-Order Logic, High Resolution, Differential Thermal Analysis, Magnetic Fields, Specific Heat, Electrical And Electronic Engineering, Superconducting magnets, Magnetic Flux, and Latent Heat
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Experimental research on mesoscopic systems puts high demands on the measurement infrastructure, including measurement system with associated sample preparation, experimental design, measurement electronics, and data collection.... more
Experimental research on mesoscopic systems puts high demands on the measurement infrastructure, including measurement system with associated sample preparation, experimental design, measurement electronics, and data collection. Successful experiments require both the ability to manufacture small samples and to successfully and accurately study their novel properties. Here, we discuss some aspects and recent advancements of general measurement techniques that should benefit
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ABSTRACT We studied the magneto-transport properties of superconductor-ferromagnet MoGe/Permalloy bilayers. The ferromagnet with stripe domain structure induces in-plane anisotropy in superconducting order parameter. Superconducting phase... more
ABSTRACT We studied the magneto-transport properties of superconductor-ferromagnet MoGe/Permalloy bilayers. The ferromagnet with stripe domain structure induces in-plane anisotropy in superconducting order parameter. Superconducting phase diagram shows that near the S-N phase boundary the superconductivity is localized in narrow mesoscopic channels just above the magnetic domain walls. By changing the in-plane direction of magnetic stripe domains it is possible to re-configure the direction of the superconducting channels and enable one to control the direction of the anisotropy axis in the superconductor.
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... The relative reduction of the average vortex spacing across the transition is about 4 3 1026 . The latent heat associated with the transition amounts to 0.65kB Tm vortex CuO2 double layer at temperatures below 88 K and drops to zero... more
... The relative reduction of the average vortex spacing across the transition is about 4 3 1026 . The latent heat associated with the transition amounts to 0.65kB Tm vortex CuO2 double layer at temperatures below 88 K and drops to zero rapidly at higher temperatures. ...
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... Carlson, K. D.; Geiser, U.; Montgomery, LK; Pyrka, GJ; Watkins, D. M.; Kommers, JM; Boryschuk, S. J.; Strieby Crouch, AV ... Daniel BBlanger* and Guylaine Laperriere Ddpartement de Chimie Universitg du Quebec d Montrdal CP 8888,... more
... Carlson, K. D.; Geiser, U.; Montgomery, LK; Pyrka, GJ; Watkins, D. M.; Kommers, JM; Boryschuk, S. J.; Strieby Crouch, AV ... Daniel BBlanger* and Guylaine Laperriere Ddpartement de Chimie Universitg du Quebec d Montrdal CP 8888, succursale A Montrdal, Qugbec, Canada ...
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Title: Peak Effect in CeRu[sub 2] and YBa[sub 2]Cu[sub 3]O[sub 7-delta]. Authors: Crabtree, GW; Kwok, WK; Fendrich, JA; Maple, MB; Herrmann, J.; Dilley, NR; Han, SH. Publication: PhysicsEssays, vol. 9, issue 4, p. 628. Publication Date:... more
Title: Peak Effect in CeRu[sub 2] and YBa[sub 2]Cu[sub 3]O[sub 7-delta]. Authors: Crabtree, GW; Kwok, WK; Fendrich, JA; Maple, MB; Herrmann, J.; Dilley, NR; Han, SH. Publication: PhysicsEssays, vol. 9, issue 4, p. 628. Publication Date: 00/1996. Origin: CROSSREF. ...
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Melting of the vortex lattice is probed directly by investigating the flow of vortices in channels created by twin boundaries. The angular dependencies of the resistivity at fixed temperatures rho(theta, T) show a clear transition from... more
Melting of the vortex lattice is probed directly by investigating the flow of vortices in channels created by twin boundaries. The angular dependencies of the resistivity at fixed temperatures rho(theta, T) show a clear transition from the vortex liquid state (maximum at rho(theta^circ, T>T_m)) to a vortex solid state (minimum at rho(theta^circ, T<T_m)) via the development of a shear modulus
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AC resistivity measurements in fields up to 8 Tesla in fully oxygenated and oxygen deficient single crystals of YBa 2 Cu 3 O 7−δ are presented. Fully oxygenated crystals show the characteristic ‘fantail’ broadening in magnetic field where... more
AC resistivity measurements in fields up to 8 Tesla in fully oxygenated and oxygen deficient single crystals of YBa 2 Cu 3 O 7−δ are presented. Fully oxygenated crystals show the characteristic ‘fantail’ broadening in magnetic field where the onset temperature remains virtually independent of the applied magnetic field and the zero resistance temperature decreases dramatically. However, in oxygen deficient crystals, the temperature dependence of the resistivity undergoes a change in shape at high magnetic fields. These results are compared with the recently discovered highest Tc=11.6 K organic superconductor κ- (ET) 2 Cu[N(CN) 2] Br where the shape of the resistive transition for H||b undergoes a change from a ‘fantail’ resistive broadening in magnetic field to that of a more conventional low Tc superconductor.
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We investigate the enhancement of vortex pinning by compound defects that are composed of correlated and point defects in a pristine untwinned YBa2Cu3O7-delta single crystal. Initial irradiation by high-energy heavy ions to a dose... more
We investigate the enhancement of vortex pinning by compound defects that are composed of correlated and point defects in a pristine untwinned YBa2Cu3O7-delta single crystal. Initial irradiation by high-energy heavy ions to a dose matching field of BPhi=2.0T increases vortex pinning via columnar defects. Subsequent proton irradiation further enhances the critical current Jc(H) by localizing the vortices near the columnar defects. Measurements of the shift of the irreversibility line for H||ab plane demonstrate that compound defects consisting of correlated and point disorder may reduce the pinning anisotropy and increase the overall critical current.
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We report a distinct thermal signature of the first-order vortex-lattice melting for the external magnetic field H both parallel and perpendicular to the c axis of an untwinned YBaâCuâO{sub 7-δ} single crystal. Latent heats and... more
We report a distinct thermal signature of the first-order vortex-lattice melting for the external magnetic field H both parallel and perpendicular to the c axis of an untwinned YBaâCuâO{sub 7-δ} single crystal. Latent heats and discontinuities in specific heat were observed for each configuration. The entropies of melting and the melting lines H{sub m}(T) both scale with an anisotropy parameter γâ8 . The specific heat of the vortex fluid is considerably larger than that of the vortex solid (by up to 2mJ/moleK² ), which is not explained by simple arguments based on counting the numbers of thermodynamic degrees of freedom. {copyright} {ital 1997} {ital The American Physical Society}
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Melting of the vortex lattice is probed directly by investigating the flow of vortices in channels created by twin boundaries. The angular dependencies of the resistivity at fixed temperatures rho(theta, T) show a clear transition from... more
Melting of the vortex lattice is probed directly by investigating the flow of vortices in channels created by twin boundaries. The angular dependencies of the resistivity at fixed temperatures rho(theta, T) show a clear transition from the vortex liquid state (maximum at rho(theta^circ, T>T_m)) to a vortex solid state (minimum at rho(theta^circ, T<T_m)) via the development of a shear modulus
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We report on a study of vortex arrangements in mesoscopic superconductors using scanning tunneling spectroscopy. Using conventional ion and electron beam lithography we defined different mesoscopic systems that confine vortex motion. The... more
We report on a study of vortex arrangements in mesoscopic superconductors using scanning tunneling spectroscopy. Using conventional ion and electron beam lithography we defined different mesoscopic systems that confine vortex motion. The spatial confinement of vortices introduces novel collective behavior that strongly depends on the size of the superconductor, the vortex density, and temperature. We will compare the experimental results
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ABSTRACT We present a study of the changes of Tc and of the upper critical field of Ba1-xKxFe2As2 that are induced by irradiation with 9 MeV protons and 1.4 GeV Pb-ions. Irradiation to a fluence of 2x10^15 protons/cm^2 creates sparse... more
ABSTRACT We present a study of the changes of Tc and of the upper critical field of Ba1-xKxFe2As2 that are induced by irradiation with 9 MeV protons and 1.4 GeV Pb-ions. Irradiation to a fluence of 2x10^15 protons/cm^2 creates sparse individual point defects and their clusters. These are sufficient to increase vortex pinning, but do not alter the phase diagram in a noticeable way. In contrast, heavy-ion irradiation to a dose matching field of 2 T induces a suppression of Tc by ˜1K and a reduction of the jump of the specific heat, deltaC, at Tc by ˜50 %. Furthermore, the upper critical field slopes increase to enormously high values of dHc2^c/dT=-12.8 T/K and dHc2^ab/dT=-21 T/K, corresponding to a low anisotropy of gamma ˜ 1.6. Such behavior is not expected for a d-wave superconductor, but is consistent with pair-breaking by non-magnetic scattering centers in a superconductor with s± gap symmetry.
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ABSTRACT A steady-state ac-temperature micro-calorimeter for heat capacity measurement of sub-microgram superconducting samples is presented. It utilizes thermocouple thermometers nano-patterned onto 150 nm thick Si3N4 membranes.... more
ABSTRACT A steady-state ac-temperature micro-calorimeter for heat capacity measurement of sub-microgram superconducting samples is presented. It utilizes thermocouple thermometers nano-patterned onto 150 nm thick Si3N4 membranes. Theoretical models, mathematical relations describing the operation of the calorimeter and calibration procedures are discussed. The system achieves a resolution of 10-4; and allows for measurements from 5 K to room temperature. The calorimeter can be continuously rotated in a split-coil magnet generating up to 8 T. To demonstrate the performance of our device we present measurements of the specific heat of single crystals of SmFeAsO0.85F0.15 (120 mum wide and 10 mum thick, crystal w1) and of BaFe2(As1-xPx)2 (150 mum wide and 30 mum thick).
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