Iron based superconductors (IBS) have interesting properties both for applications aswell as for basic research. They have very high upper critical fields (H_c2), high critical temperatures (T_c), reasonable high critical current densities (J_c). There are many different materials belonging to the iron based superconductors with the most important familiy for applications (at this moment) is the 122 (AeFe₂As₂) due to relatively easy preparation methods like Pulsed Laser Deposition (PLD) or Powder in Tube (PIT). Material properties, e.g. T_c and J_c, change with a change in Alkaline earth parent material. While some parent materials are more commonly used for application approaches (e.g. Barium) others (e.g. Europium) are interesting for basic research.
Europium (Eu) containing iron based superconductors pnictide (122) or oxypnictide family (1111) exhibit interesting physical properties. In Eu122 materials with phosphorus doping a reentrance of superconductivity occurs, aswell as a coexisting phase of superconductivity and magnetism [1]. Despite their very interesting properties in bulk form no thin films have been produced so far. The critical temperature of Eu122 is slightly lower than the critical temperature of other Alkaline earth parent materials [2] but Eu122 thin films are still relevent due to the ferromagnetic behaviour at low temperatures.
Cobalt (Co)-doped and phosphorus (P) -doped EuFe₂As₂ thin films are prepared via PLD on single crystal CaF₂ substrates and examined via X-Ray diffraction and cryogenic measurements.


[1] Ren Z, Tao Q, Jiang S, Feng C, Wang C, Dai J, Cao G and Xu Z 2009 Phys. Rev. Lett. 102 137002
[2] J Hänisch et al 2019 Supercond. Sci. Technol. 32 093001

This work is partially funded by the DFG (Deutsche Forschungsgemeinschaft) in the project HA 6407/8-1.