Demagnetizing Effects and Correction in Permeameter Measurements of Soft Magnetic Cylinders

The demagnetizing field H
_d
produced by local magnetic poles around the ends of soft magnetic cylinders magnetized in International Electrotechnical Commission type-B permeameter is studied experimentally along the major hysteresis loop M(H). The usual relation of H
_d
= -Np M is shown to be valid with a positive demagnetizing factor N
_p
<; 0.0003, but at H N ±HcJ, the intrinsic coercivity, the action of Hd is anomalously characterized by an oscillation of Np from -∞ to ∞ at H = ±H
_c
J with increasing IHI, owing to a local decrease of differential reluctance in the cylinder around where the maximum differential susceptibility occurs. These unusual demagnetizing effects make the M(H) measured at high IHI be rather accurate with often presented significant error at H N ±H
_c
J. Having an over-large measured HcJ, this error is systematic, and it may be corrected with a shift in H
_c
J and a residual demagnetizing factor ΔN
_p
<; 0.0001, if compared to demagnetizing corrected solenoid measurements of the same cylinders of large length-to-diameter ratio.