Intrinsic Properties of AFe2As2 (A = Ba, Sr) Single Crystal under Highly Hydrostatic Pressure Conditions
We measured the electrical resistivity and ac magnetic susceptibility of BaFe 2 As 2 and SrFe 2 As 2 single crystals under pressure using a cubic anvil apparatus. For BaFe 2 As 2 , the antiferromagnetic (AF) and structural transitions are suppressed with increasing pressure. Unexpectedly, these transitions persist up to 8 GPa, and no signature of a superconducting transition was observed in the pressure range investigated here. On the other hand, the AF and structural transitions of SrFe 2 As 2 collapse at around the critical pressure P C ∼5 GPa, resulting in the appearance of bulk superconductivity. The superconducting volume fraction abruptly increases above P C , and shows a dome centered at approximately 6 GPa. Our results suggest that the bulk superconducting phase competes with the AF/orthorhombic phase and only appears in the narrow pressure region of the tetragonal phase.