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Highlights

  • The Helfand and Werthamer theory developed in 1960s predicts the magnetic field at which a superconductor turns into a normal metal if certain details of the electronic structure are known.  When new superconductors are discovered, their upper critical field is usually analyzed using this theory, even though it has a well-known shortcoming — it assumes that the electronic properties of the superconductor are the same in all directions and lead to an isotropic upper...

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  • Minute chemical substitutions are used to induce superconductivity in many materials, but the precise role of these dopants in iron-pnictide superconductors is an ongoing debate. In semiconductors, doping allows charge carrier concentrations to be controlled enabling electronic devices to be created. However, dopants in iron-arsenide superconductors do not simply impact charge carrier concentrations. Recent studies show that Co or Ni substitution for iron in BaFe...

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  • Magnetism behaves very strangely in compounds of lanthanum, strontium, cobalt, and oxygen, and researchers have just attained new insight into the decades-old question of why.  Pure LaCoO3 is a non-magnetic, narrow-gap semiconductor at low temperatures.  With Strontium(Sr) doping, the magnetic properties become more prominent until, at 18% Sr, the compound becomes metallic and ferromagnetic...

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