Ferromagnetic hysteresis loop

[jackychenp]

For a ferromagnetic material in the hysteresis loop, when increasing field from H=Hc, its magnetization (M) will saturate. But if we decrease field instead, will M decreases clockwise according to the loop?

How can we make the ferromagnetic material back into the initial state (H=0, M=0)? One way is to go through TN, but some material's TN is very high. Is there any other practical method?

[berkeman]

For a ferromagnetic material in the hysteresis loop, when increasing field from H=Hc, its magnetization (M) will saturate. But if we decrease field instead, will M decreases clockwise according to the loop?

How can we make the ferromagnetic material back into the initial state (H=0, M=0)? One way is to go through TN, but some material's TN is very high. Is there any other practical method?

I'm not sure about your first question, but for the 2nd paragraph, it is common to use a "degaussing" technique to remove the residual magnetization. Degaussing uses a damped oscillatory magnetic excitation to alternately magnetize the material in opposite directions, but with a decreasing magnitude on each excursion:

http://en.wikipedia.org/wiki/Degaussing

.

[jackychenp]

Thanks.

I'm not sure about your first question, but for the 2nd paragraph, it is common to use a "degaussing" technique to remove the residual magnetization. Degaussing uses a damped oscillatory magnetic excitation to alternately magnetize the material in opposite directions, but with a decreasing magnitude on each excursion:

http://en.wikipedia.org/wiki/Degaussing

.