Magnetization Process

Bm Recoil induction

, is the magnetic induction that remains in a magnetic material after 

magnetizing and conditioning for final use; measured in gauss. 

 

Bo Magnetic induction

, at the point of the maximum energy product (BH)max; measured in 

gauss. 

 

Br Residual induction (or flux density)

, is the magnetic induction corresponding to 

zero magnetizing force in a magnetic material after saturation in a closed circuit; measured in 

gauss. 

 

f Reluctance factor

, accounts for the apparent magnetic circuit reluctance. This factor is 

required due to the treatment of Hm and Hg as constants. 

 

F Leakage factor

, accounts for flux leakage from the magnetic circuit. It is the ratio between 

the magnetic flux at the magnet neutral section and the average flux present in the air gap.  

 

F = (BmAm)/(BgAg) 

 

F Magnetomotive force

, (magnetic potential difference), is the line integral of the field 

strength, H, between any two points, p

1

 and p

2

. 

 

p

1

 

F =  

∫

 H dl 

p

2

 

 

F = magnetomotive force in gilberts 

H = field strength in oersteds 

dl = an element of length between the two points, in centimeters. 

 

H Magnetic field strength

, (magnetizing or demagnetizing force), is the measure of the 

vector magnetic quantity that determines the ability of an electric current, or a magnetic body, to 

induce a magnetic field at a given point; measured in oersteds. 

 

Hc Coercive force of a material

, is equal to the demagnetizing force required to reduce 

residual induction, B, to zero in a magnetic field after magnetizing to saturation; measured in 

oersteds. 

 

Hci Intrinsic coercive force of a material

, indicates its resistance to demagnetization. It 

is equal to the demagnetizing force which reduces the intrinsic induction, Bi, in the material to 

zero after magnetizing to saturation; measured in oersteds. 

 

Hd

 is that value of H corresponding to the remanent induction, Bd; measured in oersteds. 

 

Hm

 is that value of H corresponding to the recoil induction, Bm; measured in oersteds. 

 

Ho

 is the magnetic field strength at the point of the maximum energy product (BH)max; 

measured in oersteds. 

 

Hs Net effective magnetizing force

, is the magnetizing force required in the material, to 

magnetize to saturation measured in oersteds. 

 

J

, see Bi, Intrinsic induction. 

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Js

, see Bis Saturation intrinsic induction. 

 

lg Length of the air gap

, is the length of the path of the central flux line of the air gap; 

measured in centimeters. 

 

lm Length of the magnet

, is the total length of magnet material traversed in one complete 

revolution of the center line of the magnetic circuit; measured in centimeters. 

 

lm/D Dimension ratio

, is the ratio of the length of a magnet to its diameter, or the diameter 

of a circle of equivalent cross-sectional area. For simple geometries, such as bars and rods, the 

dimension ratio is related to the slope of the operating line of the magnet, Bd/Hd. 

 

P Permeance

, is the reciprocal of the reluctance, R, measured in maxwells per gilbert. 

 

R Reluctance

, is somewhat analogous to electrical resistance. It is the quantity that 

determines the magnetic flux, 

φ

, resulting from a given magnetomotive force, F. 

 

R = F/

φ

 

 

R = reluctance, in gilberts per Maxwell 

F = magnetomotive force, in gilberts 

φ

 = flux, in Maxwells 

 

Tc, Curie temperature

, is the transition temperature above which a material loses its 

magnet properties. 

 

Tmax Maximum service temperature

, is the maximum temperature to which the magnet 

may be exposed with no significant long range instability or structural changes. 

 

Vg Air gap volume

, is the useful volume of air or non-magnetic material between magnetic 

poles; measured in cubic centimeters. 

 

μ

 permeability

, is the general term used to express various relationships between magnetic 

induction, B, and the field strength, H. 

 

μ

re recoil permeability

, is the average slope of the recoil hysteresis loop. Also known as a 

minor loop. 

 

φ

 magnetic flux

, is a contrived but measurable concept that has evolved in an attempt to 

describe the "flow" of a magnetic field. Mathematically, it is the surface integral of the normal 

component of the magnetic induction, B, over an area, A. 

 

A closed circuit

 condition exists when the external flux path of a permanent magnet is 

confined with high permeability material. 

 

The demagnetization curve

 is the second (or fourth) quadrant of a major hysteresis loop. 

Points on this curve are designated by the coordinates Bd and Hd 

 

A Fluxmeter

 is an instrument that measures the change of flux linkage with a search coil. 

 

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