Hole doping by pressure on the 1111 pnictides CaFeAsF and SrFeAsF

D.C. FREITAS; G. GARBARINO; RUBEN WEHT; A. SOW; X. ZHU; F. HAN; P. CHENG; J. JU; H.H. WEN; MANUEL NÚÑEZ-REGUEIRO

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Lugar: Londres; Año: 2014 vol. 26 p. 5702 - 5702

0953-8984

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 ofstructure 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 thedevelopment 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.