title: Hole doping by pressure on the 1111 pnictides CaFeAsF and SrFeAsF.
abstract: 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.
authors.affiliation: Institut Néel, Centre National de la Recherche Scientifique (CNRS) & Université Joseph Fourier (UJF), 25 Avenue des Martyrs, BP166, F-38042 Grenoble Cedex 9, France.
authors.forename: Daniele C
authors.initials: DC
authors.lastname: Freitas
authors.forename: Gastón
authors.initials: G
authors.lastname: Garbarino
authors.forename: Ruben
authors.initials: R
authors.lastname: Weht
authors.forename: Amadou
authors.initials: A
authors.lastname: Sow
authors.forename: Xiyu
authors.initials: X
authors.lastname: Zhu
authors.forename: Fei
authors.initials: F
authors.lastname: Han
authors.forename: Peng
authors.initials: P
authors.lastname: Cheng
authors.forename: Jing
authors.initials: J
authors.lastname: Ju
authors.forename: Hai Hu
authors.initials: HH
authors.lastname: Wen
authors.forename: Manuel
authors.initials: M
authors.lastname: Núñez-Regueiro
mesh_terms: D001152:Arsenicals / Q000737:chemistry*; D001274:Atmospheric Pressure; D017610:Calcium Compounds / Q000737:chemistry*; D004553:Electric Conductivity; D005296:Ferrous Compounds / Q000737:chemistry*; D008956:Models, Chemical; D044367:Phase Transition; D013324:Strontium / Q000737:chemistry*; D044366:Transition Temperature; D014961:X-Ray Diffraction
chemical_list: D001152:Arsenicals; D017610:Calcium Compounds; D005296:Ferrous Compounds; D013324:Strontium