Superconductivity in magnetically doped SrTiO3

Abstract

Doped SrTiO 3 is a superconductor whose pairing mechanism is still not fully understood. The response of a superconductor to impurities has long been used to obtain insights into the nature of the superconducting state. Here, the superconductivity of SrTiO 3 films that are doped or alloyed with different rare earth ions, which carry a magnetic moment, is investigated. It is shown that large concentrations (up to a few percent) of rare earth ions with unpaired f-electrons, such as Sm and Eu, do not reduce the superconducting critical temperature and critical fields. The finding is independent of whether the rare earth ion acts as a dopant or is an isovalent impurity. The interactions between the superconducting condensate and the magnetic dopants that could result in the observed insensitivity to magnetic impurities are discussed.

Superconductivity enhancement in polar metal regions of Sr0.95Ba0.05TiO3 and Sr0.985Ca0.015TiO3 revealed by systematic Nb doping

“…In contrast, electron doping of SrTiO 3 , e.g., substitution of La 3+ or Sm 3+ for Sr 2+ (refs. [4][5][6][7]42,43 ) or Nb 5+ for Ti 4+ (refs. 21,[44][45][46][47][48] ), or removal of O 2− (refs.…”

“…4[,9,10 ), was found to raise the transition temperature T c to be higher than that of the SrTiO 3 matrix, indicating that the superconductivity appears to be enhanced in the ferroelectric SrTiO 3 . Several experimental investigations of SrTiO 3 with epitaxial strain were also noteworthy [5][6][7]43 ; the strain breaks the material's spatial inversion symmetry and enhances the spin-orbit interactions 5,6 , and T c then increased to 0.6 K (ref. 5 ).…”

“…Surprisingly, although T c is very low in these SrTiO 3 systems, magnetic impurities, e.g., Sm, Eu, demonstrated no effect on T c (ref. 43 ).…”

Polar Metals Taxonomy for Materials Classification and Discovery

“…For example, Jiao et al describe separating polar metals with magnetic ordering temperatures into "type-I" and "type-II" categories depending on the strength of the coupling between magnetic and polar orders, with Pb 2 CoOsO 6 being an example of a "type-II" magnetic polar metal [81]. By contrast, the magnetic ordering predicted in SrCaRu 2 O 6 is not expected to couple to the inversion-lifting distortion [8], or one might note the insensitivity of the polar transition in doped SrTiO 3 to the presence of magnetic doping and isovalent substitution as an example of "type-I" behavior [103]. Still, we may describe other categories, including magnetically-driven metal-insulator transitions in Pb 2 CaOsO 6 [104] and Bsite substituted Ca 3 Ru 2 O 7 [105][106][107] (in which case the magnetic and transport properties are highly sensitive to dilute concentrations and dependent on the substituting species-Mn, Ti, or Fe).…”

Functional properties of Sr1-xGdxTiO3 ceramics synthesized by solid state reaction method

“…Recently, the researchers worked on the trivalent rare Earth materials (Dy 3+ , Sm 3+ , Pr 3+ , Nd 3+ , etc) to modify the characteristics of STO ceramics by altering the oxygen vacancies [41][42][43][44][45][46][47][48][49][50][51][52]. Despite reports of lowtemperature dielectric relaxation in RE-doped STO systems as a result of lattice distortion, one may question whether this phenomenon is related to oxygen vacancies.…”