Resonant peak in the density of states in normal-metal/diffusive-ferromagnet/superconductor junctions

The conditions for the formation of zero-energy peak in the density of states (DOS) in the normal metal/insulator/diffusive ferromagnet/insulator/s-wave superconductor (N/I/DF/I/S) junctions are studied by solving the Usadel equations. The DOS of the diffusive-ferromagnet conductor (DF) is calculated in various regimes for different magnitudes of the resistance, Thouless energy, and the exchange field of the DF, as well as for various resistances of the insulating barriers. The conditions for the DOS peak are formulated for the cases of weak proximity effect [large resistance of the diffusive-feromagnet/superconductor (DF/S) interface] and strong proximity effect (small resistance of the DF/S interface).