Co and Mn doping effect in polycrystalline (Ca,La) and (Ca,Pr)FeAs₂superconductors

Abstract

Superconducting properties of Co-co-doped (Ca,RE)FeAs 2 ((Ca,RE)112: RE = La, Pr) were investigated. Co-co-doping increased T c of (Ca,Pr)112 while Mn-co-doping suppressed superconductivity of (Ca,RE)112. Co-co-doped (Ca,La)112 showed large diamagnetic screening and sharper superconducting transition than Co-free (Ca,La)112. T c zero observed in resistivity measurements increased from 14 K to 30 K by Co-co-doping, while T c onset was not increased.The critical current density (J c ) of Co-co-doped (Ca,La)112 were approximately 2.1 x 10 4 Acm -2 and 3.2 x 10 3 Acm -2 at 2 K and 25 K, respectively, near zero field. These relatively high J c s and large diamagnetic screening observed in susceptibility measurement as for polycrystalline bulks suggest bulk superconductivity of Co-co-doped (Ca,RE)112 compounds.

Second magnetization peak effect, vortex dynamics and flux pinning in 112-type superconductor Ca0.8La0.2Fe1−xCoxAs2

“…Unfortunately, due to the relatively poor superconductivity (SC) in the previously grown 112-type crystals313233, no detailed magnetization analysis has been performed. Recently, Co doping has been used to improve the superconducting properties of 112-type polycrystals34 In this work, we report a large superconducting critical current J s over 2*10 6  A/cm 2 in our Co-co-doping 112-type superconductor Ca 0.8 La 0.2 Fe 1− x Co x As 2 single crystal. We found a well pronounced SMP effect in the field-dependent magnetization measurement of our sample, which, to our knowledge, has not yet been reported.…”

Two-band and pauli-limiting effects on the upper critical field of 112-type iron pnictide superconductors

“…The slightly wide superconducting transition for Ca 0.83 La 0.17 FeAs 2 seems to be a general feature in this compound, which may result from the inhomogeneity of La distribution. Upon a small amount of Co doping, single crystal quality can be improved significantly with sharp superconducting transition and large superconducting volume fraction20212223.…”

“…Previous studies of μ 0 H c2 ( T ) were just performed near T c in low magnetic field2021. Thus, measurement in higher magnetic field is essential to clarify the behavior of upper critical field and its anisotropy γ at low temperature region in this new type IBSs.…”

Superconductivity and Dirac fermions in 112‐phase pnictides

“…Polycrystalline samples were synthesized using solid state reaction inside a high‐pressure cell . For CaFeAs 2 ( RE = rare earths from LaGd) synthesis (), a mixture of FeAs, RE As, Ca, and As powders were mixed and pelletized which was later allowed to react inside a boron nitride crucible between 1000 and 1200C for 1 h under 2 GPa pressure . Sala () pointed out that high pressure for synthesis is essential to incorporate smaller RE ‐ions and at much higher pressure (2 GPa) doping of Tb, Dy, Ho, and Y into the 112‐phase could be possible.…”

“…In the past two years, research interest again increased for due to the availability of single crystals, high’ in the bulk phase, and the possibility of a range of substitutions. Significant amount of research work was done earlier in other 112‐type materials like LaPd x Sb 2 (), LaPd x Bi 2 , CeNi x Sb 2 , LaNi x Sb 2 , etc.…”