Why is soft iron used in a solenoid? What makes it special to be used particularly?

Usually an electromagnet or a temperorary magnet is prepared by placing a soft iron core in a solenoid.A strong field can be made by coiling the wire around a piece of soft iron. An electromagnet shows magnetic properties only when  electric current flows through the solenoid or coil.

 

The soft iron inside the coil becomes a magnet when current flows through the coil and it makes the magnetic field stronger.Soft iron is a material which has a less capacity to retain magnetic property in itself and it looses all its magnetism when current in the coil stops flowing. Soft iron thus forms a temperory magnet which can be switched on and off depending on the current flow.On the other hand if steel was used instead of soft iron, it forms a permanet magnet as it would continue to behave as a magnet even when the current flow is stopped.