Ultrasonic-assisted surfactant-free synthesis of highly magnetized FeCo alloy nanocrystallite from ferric and cobalt salt

► Crystalline FeCo alloys nanoparticles synthesized by a ultrasonic-assisted surfactant-free route. ► Using inexpensive hydrated ferric salts (FeCl3·6H2O) as iron precursors. ► Ultrasound wave has good effects on the FeCo crystallization. ► Fe59Co41 nanocrystallite shows excellent soft magnetic behavior with high saturation magnetization up to 216 emu/g.