Pressure effect on iron based superconductors

A tuning of macroscopic thermo dynamical parameters such as temperature, pressure and volume play a crucial role in strongly correlated electron systems especially high Tc superconductors, which leads to increasing conductivity as well as effective way of reducing intrinsic magnetic moments. Application of chemical and external pressure exhibits significant increases of critical temperature of recently discovered iron pnictides and chalcogenides superconductors. In this present report, we have investigated hydrostatic pressure effects on resistivity and magnetization of some 1111 type based oxypnictide superconductors such as Co doped CeFeAsO, La0.8Th0.2FeAsO, Ce0.6Y0.4FeAsO0.8F0.2 and Yb doped CeFeAsO systems respectively. The initially applied pressure increases the Tc and its down to lower value when beyond increasing pressure also has been observed and pressure effects on crystal structure were also discussed. From that all the obtained results reveal that controlling of magnetic instability and structure distortion at higher pressure is a dominant way to further developing of Tc of these new ferropnictides compounds. (author)