High pressure studies on Fe-pnictide superconductors

A review of high pressure studies on Fe-pnictide superconductors is given. The pressure effects on the magnetic and superconducting transitions are discussed for different classes of doped and undoped FeAs-compounds: ROFeAs (R = rare-earth), AeFe(2)As(2) (Ae = Ca, Sr, Ba), and AFeAs (A = Li, Na). Pressure tends to decrease the magnetic transition temperature in the undoped or only slightly doped compounds. The Superconducting Tc increases with low pressure for uderdoped FeAs-pnictides, remains approximately constant for optimal doping, and decreases linearly in the overdoped range. The undoped LaOFeAs and AeFe(2)As(2) become superconducting under pressure although non-hydrostatic pressure condition seems to play a role in CaFe2As2. The Superconductivity in the (undoped) AFeAs is explained as a chemical pressure effect due to the Volume contraction caused by the small ionic size of the A-elements. The binary FeSe shows the largest pressure coefficient of Tc in the Se-deficient superconducting phase. (C) 2009 Elsevier B.V. All rights reserved.