R. A. Hein

Bulk superconductivity above 100 K in the TlSrCaCu system

Abstract We report the synthesis and physical properties of a new copper-oxide superconductor, TlSrCaCuoxide. We have found that samples of this material exhibit zero electrical resistance below 105 K. DC susceptibility measurements show evidence of bulk superconductivity with diamagnetic onsets at 119 K and 70 K. X-ray diffraction data are compatible with the basic perovskite structure and can be indexed to a tetragonal lattice with unit cell parameters of a = 3.805 ± 0.006 A and c = 12.14 ± 0.06 A .

Superconducting behavior of A15 compounds

Abstract Superconductivity has been discovered in the A15 compounds V 1− x Ni x , V 3 Pd and Ta 85 Pt 15 and a new feature has been observed in the T c vs. e/a correlation for A15 compounds. The anomalously low T c of V 3 Pd is attributed to magnetic interconnections. Critical magnetic field data is presented for Nb 3 Os, Cr 3 Rh and Cr 3 Ir.

Superconducting properties of PbxSn1−xTe

Abstract Superconducting transition temperatures and critical magnetic field curves on low carrier concentration Pb x Sn 1− x Te samples where 0.25 ⩽ x ⩽0.55 are reported. These data are interpreted in terms of a changing band structure from that of SnTe to one which is similar to that of GeTe. The importance of carriers (holes) in secondary maxima of the valence band is emphasized.

Superconducting Intermetallic Compounds — The A15 Story

Twenty years ago the phenomenon of superconductivity was the exclusive property of the low temperature physicist and was regarded as the major unsolved problem of solid state physics. Today one reads and hears that superconductivity is well understood and that most solid state theoreticians regard it as a “solved problem” no longer worthy of their full attention. I believe that, due to the technological promises of applied superconductivity, there are currently more metallurgists, engineers and electronic specialists involved with superconductivity than there are physicists, or at least physicists who are engaged in the “physics” of superconductivity.

Superconductivity of Thorium below l°k

The critical magnetic field of thorium has been determined between 0.1 and 1.37 deg K, the transition temperature, where the initial slope of the critical field curve is 190 gauss/deg. The data indicate a value of 162 gauss for the critical field at absolute zero. The critical field curve departs from a parabola near the transition temperature. The electronic specific heat, 11.1 h 10/sup -4/T cal/mole-deg, deduced from the magnetic measurements is in substantial agreement with the previously determined calorimetric value. (auth)

A Coupled Structural and Electrical Transition in La2CuO4 Near 30 K

Recently there has been an explosion of activity focused on the new class of oxygen defect, perovskite related, copper oxide superconductors. All of this was initiated by the discovery of superconductivity at temperatures in excess of 30 K in La-Ba-Cu-oxides[1] and the subsequent discovery of superconductivity in excess of 90 K in Y-Ba-Cu-oxides.[2] The prototypical compound for the lower transition temperature materials is La2CuO4 which, at room temperature, crystallizes in an orthorhombic distortion of the K2NiF4-structure. [3,4] It has recently been shown that the superconducting compounds La2−xMxCuO4, where M = Ba, Ca, or Sr, are also orthorhombic above TC.[5,6]