Probes for bulk superconductivity in iron pnictide systems under hydrostatic pressure conditions

We discuss the sensitivity of iron based superconductors to the hydrostaticity of pressure conditions, which results in discrepancies between different studies. To clarify the situation we present the phase diagram of several systems obtained on single crystals, using the highly hydrostatic pressure conditions of argon in a diamond anvil cell, and an ac susceptibility method to detect superconductivity.