Zeeman-limited Superconductivity in Crystalline Al Films

We report the evolution of the Zeeman-mediated superconducting phase diagram (PD) in ultra-thin crystalline Al films. Parallel critical field measurements, down to 50 mK, were made across the superconducting tricritical point of films ranging in thickness from 7 ML to 30 ML. The resulting phase boundaries were compared with the quasi-classical theory of a Zeeman-mediated transition between a homogeneous BCS condensate and a spin polarized Fermi liquid. Films thicker than $\sim$20 ML showed good agreement with theory, but thinner films exhibited an anomalous PD that cannot be reconciled within a homogeneous BCS framework.Comment: 8 pages, 9 figure

COMBINING ECONOMIC AND BIOLOGICAL DATA TO ESTIMATE THE IMPACT OF POLLUTION ON CROP PRODUCTION

Duality methods utilizing a profit function framework are employed to estimate the output elasticity of ambient ozone levels on cash grain farms in Illinois. While duality methods have been recommended as a cure to many of the statistical problems of direct estimation of production functions, multicollinearity may still be a problem. A method for utilizing stochastic information on parameters of a seemingly unrelated system of equations, which is implied by profit function estimation, is developed and applied to measuring the impact of ozone. Such an approach may be necessary in measuring other environmental effects because of a lack of regressor variability.Crop Production/Industries, Environmental Economics and Policy,

A novel procedure for fast surface structural analysis based on LEED intensity data

By evaluating LEED intensities from different diffraction beams taken only at discrete energy intervals (which may be as large as 15–20 eV) the same degree of reliability in surface structure determination can be reached as with the conventional techniques based on analysis of continuous I/V-spectra. The minimum of the corresponding R-factor can be found by a least-squares fit method, as will be exemplified with a system in which 8 structural parameters were subject to simultaneous refinement

Effect of Partial Substitution of Ni by Co on the Magnetic and Magnetocaloric Properties of Ni\u3csub\u3e50\u3c/sub\u3eMn\u3csub\u3e35\u3c/sub\u3eIn\u3csub\u3e15\u3c/sub\u3e Heusler Alloy

The magnetic and magnetocaloric properties of Ni48Co2Mn35In15 were studied using magnetization and heat capacity measurements. The magnetic entropy change (Delta SM) was evaluated from both magnetizing and demagnetizing fields. An inverse Delta SM for the magnetizing and demagnetizing processes were found to be 20.5 and 18.5 J kg-1 K-1, respectively, for Delta H = 5 T at the martensitic transition (T=TM). The normal Delta SM was found to be -5.4 J kg-1 K-1 for both fields at the paramagnetic/ferromagnetic transition (T=TC). The effective refrigeration capacity at TM and TC for magnetizing field was found to be 268 and 243 J/kg (285 and 243 J/kg for the demagnetizing field), respectively. We have also estimated the density of states, the Debye temperature, and the inverse adiabatic temperature change to be 4.93 states/eV f.u., 314 K, and -3.7 K, respectively, from the measured heat capacity data

Effect of partial substitution of Ni by Co on the magnetic and magnetocaloric properties of Ni50Mn35In15 Heusler alloy

The magnetic and magnetocaloric properties of Ni48Co 2Mn35In15 were studied using magnetization and heat capacity measurements. The magnetic entropy change (δSM) was evaluated from both magnetizing and demagnetizing fields. An inverse S M for the magnetizing and demagnetizing processes were found to be 20.5 and 18.5 J kg-1 K-1, respectively, for δH 5 T at the martensitic transition (T TM). The normal SM was found to be -5.4 J kg-1 K-1 for both fields at the paramagnetic/ferromagnetic transition (T = TC). The effective refrigeration capacity at TM and TC for magnetizing field was found to be 268 and 243 J/kg (285 and 243 J/kg for the demagnetizing field), respectively. We have also estimated the density of states, the Debye temperature, and the inverse adiabatic temperature change to be 4.93 states/eV f.u., 314 K, and -3.7 K, respectively, from the measured heat capacity data. © 2011 American Institute of Physics

Mn1-xFexCoGe: A strongly correlated metal in the proximity of a noncollinear ferromagnetic state

An unusually large Kadowaki-Woods ratio of A/γ2 ∼ 43 μΩ·cm·mol2·K2·J -2 has been observed for intermetallic Mn1-xFe xCoGe compounds in the proximity of x = 0.2 where the magnetic state of itinerant electrons system changes. The ratio is approximately four times larger than observed for heavy fermion systems. The manifestation of the strong electron correlations can be realized from the anisotropic origin of the effect through the substantial reduction of interlayer transport of heavy quasiparticles with comparable mean-free path and interlayer spacing in the proximity of a noncollinear ferromagnetic state associated with a large density of states at the Fermi level. © 2013 AIP Publishing LLC

Mn\u3csub\u3e1-x\u3c/sub\u3eFe\u3csub\u3ex\u3c/sub\u3eCoGe: A Strongly Correlated Metal in the Proximity of a Noncollinear Ferromagnetic State

An unusually large Kadowaki-Woods ratio of A/gamma2 similar to 43 mu Omega.cm.mol2.K2.J-2 has been observed for intermetallic Mn1-xFexCoGe compounds in the proximity of x = 0.2 where the magnetic state of itinerant electrons system changes. The ratio is approximately four times larger than observed for heavy fermion systems. The manifestation of the strong electron correlations can be realized from the anisotropic origin of the effect through the substantial reduction of interlayer transport of heavy quasiparticles with comparable mean-free path and interlayer spacing in the proximity of a noncollinear ferromagnetic state associated with a large density of states at the Fermi level

The influence of hydrostatic pressure on the magnetic and magnetocaloric properties of DyRu2Si2

We report the magnetic and magnetocaloric properties of the tetragonal rare-earth compound DyRu2Si2 under applied hydrostatic pressure. The isothermal entropy change (ΔS) and the adiabatic temperature change (ΔTad) were calculated from magnetization data collected at different applied pressures and from heat capacity measurements conducted at atmospheric pressure, respectively. The application of hydrostatic pressure significantly modified the multi-step magnetization curve and the saturation magnetization. A suppression of the magnetization was observed for P = 0.588 GPa and P = 0.654 GPa whereas, at about P ≈1 GPa, the saturation magnetization increased and the magnetization isotherms again resembled the curves measured at atmospheric pressure. A small thermal hysteresis was observed between the heating and cooling M(T) curves at Tt=3.4 K, with an applied magnetic field of H = 0.1 T. This thermal hysteresis indicates a first-order like transition which was also supported by the Arrott plot analysis. The volume magnetostriction was estimated from the pressure-dependent magnetization measurements using a Maxwell relation

Geometric quenching of orbital pair breaking in a single crystalline superconducting nanomesh network

In a superconductor Cooper pairs condense into a single state and in so doing support dissipation free charge flow and perfect diamagnetism. In a magnetic field the minimum kinetic energy of the Cooper pairs increases, producing an orbital pair breaking effect. We show that it is possible to significantly quench the orbital pair breaking effect for both parallel and perpendicular magnetic fields in a thin film superconductor with lateral nanostructure on a length scale smaller than the magnetic length. By growing an ultra-thin (2 nm thick) single crystalline Pb nanowire network, we establish nm scale lateral structure without introducing weak links. Our network suppresses orbital pair breaking for both perpendicular and in-plane fields with a negligible reduction in zero-field resistive critical temperatures. Our study opens a frontier in nanoscale superconductivity by providing a strategy for maintaining pairing in strong field environments in all directions with important technological implications

Ultrathin two-dimensional superconductivity with strong spin-orbit coupling

We report on a study of epitaxially grown ultrathin Pb films that are only a few atoms thick and have parallel critical magnetic fields much higher than the expected limit set by the interaction of electron spins with a magnetic field, that is, the Clogston-Chandrasekhar limit. The epitaxial thin films are classified as dirty-limit superconductors because their mean-free paths, which are limited by surface scattering, are smaller than their superconducting coherence lengths. The uniformity of superconductivity in these thin films is established by comparing scanning tunneling spectroscopy, scanning superconducting quantum interference device (SQUID) magnetometry, double-coil mutual inductance, and magneto-transport, data that provide average superfluid rigidity on length scales covering the range from microscopic to macroscopic. We argue that the survival of superconductivity at Zeeman energies much larger than the superconducting gap can be understood only as the consequence of strong spin-orbit coupling that, together with substrate-induced inversionsymmetry breaking, produces spin splitting in the normal-state energy bands that is much larger than the superconductor\u27s energy gap