Magnetic susceptibility () is given by formula

..(i)

When a ferromagnetic material goes through a hysteresis loop

At point C:

Magnetic intensity H becomes 0 whereas magnetization I is finite.

From(i) we get

At point G:

Magnetization I, becomes 0 whereas H is finite

From(i) we get

In the second quadrant H is negative whereas I is positive therefore

Becomes negative here

Therefore, when a ferromagnetic material goes through hysteresis loop the magnetic susceptibility may be zero, may be negative and may be infinity.