Visualization of the magnetic flux structure in phosphorus-doped EuFe2As2 single crystals

Resumo

Magnetic flux structure on the surface of EuFe₂(As_1-xP_x)₂ single crystals with nearly optimal phosphorus doping levels x = 0.20 and x = 0.21 is studied by low-temperature magnetic force microscopy and decoration with ferromagnetic nanoparticles. The studies are performed in a broad temperature range. It is shown that the single crystal with x = 0.21 in the temperature range between the critical temperatures T_SC= 22 K and T_C = (18 ± 0.3) K of the superconducting and ferromagnetic phase transitions, respectively, has the vortex structure of a frozen magnetic flux, typical for type-II superconductors. The magnetic domain structure is observed in the superconducting state below T_C. The nature of this structure is discussed.