Magnetic, Transport Properties, Lower Critical Field, Penetration Depth, Anisotropy and Gap Evidences of Ca$_{10}$ (Pt$_{n}$as$_{8})$ (Fe$_{2-X}$Pt$_{x}$As$_{2})_{5}$(n $=$ 3 And 4) Superconductors

Platinum iron arsenides Ca$_{10}$(Fe$_{1-x}$Pt$_{x}$As)$_{10}$(Pt$_{n}$As$_{8})$ ($n~=$ 3 {\&} 4) are first Fe based superconductors with metallic spacer layers. Crystal structure have stacks of Ca (Pt$_{n}$As$_{8})$ Ca (Fe$_{2}$As$_{2})$ consists of superconducting Fe$_{2}$As$_{2}$ layers alternating with Pt$_{n}$As$_{8}$ layers, forming a triclinic \textit{P1}, 1038phase with $n = $ 3 and tetragonal \textit{P4/n}, 1048phase with $n = $ 4. Two different negatively charged layers [(FeAs)$_{10}$]$^{n-}$ and (Pt$_{3+y}$As$_{8})^{m-}$ compete for electrons provided by Ca$^{2+}$-ions. In parent compound Ca$_{10}$(FeAs)$_{10}$(Pt$_{3}$As$_{8})$, no excess charge dopes FeAs-layer, and superconductivity is induced by Pt-substitution. Additional Pt in Pt$_{4}$As$_{8}$ layer shifts charge balance between layers and T$_{c}$ raises to 38 K, but decreases again if additionally Pt is substituted for Fe. Charge doping is supported by T$_{c}$ $\approx $ 30 K in electron-doped La-1038, x $=$ 0:2 (Ca$_{1-x}$La$_{x})_{10}$(Pt$_{3}$As$_{8})$(Fe$_{2}$As$_{2})_{5}$ without significant Pt-substitution. Magnetic properties were explored. Magnetization measurements reveal fish-tail hysteresis loop and relatively high critical current density at low $T$. Lower critical field,$ H_{c1}$~deduced from vortex penetration into single crystals. Ginsburg-Lauder parameters extracted from reversible magnetizations data. Upper critical field determined by resistive transition shows large anisotropy. With La doping, the structural/magnetic phase transitions are suppressed. $T$ dependency of the $H_{c1}$ is compared with BCS-gap models and anisotropy of $H_{c1}$ will be discussed.