Theory of Long Period Magnetic Relaxation

A discussion is given of the long period changes in magnetization in a mild steel specimen subjected to alternating stresses while in a weak magnetic field. The magnetization changes appear to occur with two time constants, of the order of three months and five years. A formal treatment of the phenomena is given along the lines of the time-dependent barrier potential used by Snoek in discussing other magnetic relaxation processes. The increase in the potential barrier is pictured as caused by the mechanical relaxation of local strains.