  By substituting Fe with the 5d-transition metal Pt in BaFe2As2, we have
successfully synthesized the superconductors BaFe2-xPtxAs2. The systematic
evolution of the lattice constants indicates that the Fe ions were successfully
replaced by Pt ions. By increasing the doping content of Pt, the
antiferromagnetic order and structural transition of the parent phase is
suppressed and superconductivity emerges at a doping level of about x = 0.02.
At a doping level of x = 0.1, we get a maximum transition temperature Tc of
about 25 K. The synchrotron powder x-ray diffraction shows that the resistivity
anomaly is in good agreement with the structural transition. The
superconducting transitions at different magnetic fields were also measured at
the doping level of about x = 0.1, yielding a slope of -dHc2/dT = 5.4 T/K near
Tc. A phase diagram was established for the Pt doped 122 system. Our results
suggest that superconductivity can also be easily induced in the FeAs family by
substituting the Fe with Pt, with almost the similar maximum transition
temperatures as doping Ni, Co, Rh and Ir.
