Hole doping by pressure on the 1111 pnictides CaFeAsF and SrFeAsF

Daniele-Cristina Silva-De-Freitas , Gastón Garbarino (1) , Ruben Weht (2) , Amadou Sow , X. Zhu (3) , F. Han (3) , P. Cheng (3) , J. Ju (3) , H.H. Wen (4) , Manuel Nunez-Regueiro (5)

1 ESRF - European Synchrotron Radiation Facility
2 CNEA - Comisión Nacional de Energía Atómica [ARGENTINA]
3 CAS - Chinese Academy of Sciences [Beijing]
4 beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science
5 NEEL - MagSup - Magnétisme et Supraconductivité

We determine the pressure phase diagram of the 1111 compounds CaFeAsF and SrFeAsF, up to 20 GPa and down to 4 K by electrical resistivity measurements and the change of structure up to 40 GPa at room temperature. The antiferromagnetic transition temperature, as determined by the derivative peak, shows a minimum at ~5 GPa (10 GPa) for the Ca (Sr) compound. For CaFeAsF, superconductivity appears at this minimum, coincident with the development of a previously reported monoclinic phase. For SrFeAsF, where the orthorhombic and the monoclinic phase were reported to coexist, superconductivity exists above P≥1 GPa. Both phase diagrams can be scaled by a shift of ~10 GPa pressure at which the volume of SrFeAsF and that of CaFeAsF at ambient pressure coincide. The difference of our phase diagram with that of electron-doped 1111 samples is accounted for by hole doping under pressure, which we verified through electron band structure calculations.

Domaines: Supraconductivité [cond-mat.supr-con]

Daniele-Cristina Silva-De-Freitas, Gastón Garbarino, Ruben Weht, Amadou Sow, X. Zhu, et al.. Hole doping by pressure on the 1111 pnictides CaFeAsF and SrFeAsF. Journal of Physics: Condensed Matter, 2014, 26 (15), pp.155702. ⟨10.1088/0953-8984/26/15/155702⟩. ⟨hal-01002142⟩