Pressure-Induced Magnetism In The Iron-Based Superconductors Afe(2)As(2) (A = K, Cs, Rb)

The magnetic properties of iron-based superconductors AFe(2)As(2) (A = K, Cs, and Rb), which are characterized by the V-shaped dependence of the critical temperature (T-c) on pressure (P), were studied by means of the muon spin rotation/relaxation technique. In all three systems studied the magnetism was found to appear for pressures slightly below the critical one (P-c), i.e., at pressure where T-c(P) changes the slope. Rather than competing, magnetism and superconductivity in AFe(2)As(2) are coexisting at the P greater than or similar to P-c pressure region. Our results support the scenario of a transition from one pairing state to another, with different symmetries on either side of P-c.