Why is there higher inductance with Iron cores?

Inductors store energy by means of a magnetic field. The flow of electric current creates a magnetic field around the inductor. The strength depends on the magnitude of the current and follows any changes in current. Iron has a very high magnetic permeability. The greater the permeability of the core will result in a greater magnetic flux. When there is a larger flux there will a larger magnetic force and thus creating a much larger inductance.