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In view of the confusion with regard to the units sometimes seen in our journals, the Editorial Committee of the Magnetics Society of Japan has decided to present a recommendation concerning the units to be used in the journals. We propose the international system of units (SI) as the recommended system of units in our journals, in accordance with international trends. Regrettably, however, the change over to SI has been slower in the field of magnetism than in other fields. In view of this situation, we recommend SI but do not refuse to accept the use of other unit systems such as the cgs unit system. However, mixed use of them should be avoided. We ask you to use SI units with reference to the conversion tables below (Tables 1 to 3).
Table 1 Conversion table to SI for magnetism related properties.
| Quantity |
Symbol |
cgs-Gauss units
B = H + 4 M) |
Conversion
factor to SI |
MKSA units
(E-H cor.)
B =  0 H + I |
Conversion
factor to SI |
SI
(E-B cor.)
B = 0 (H + M ) |
| Magnetic flux
density |
B |
G |
10-4 |
T, Wb/m2 |
1 |
T, Wb/m2 |
| Magnetic flux |
 |
Mx |
10-8 |
Wb |
1 |
Wb |
| Magnetomotive
force |
V m |
Gb |
10/4 |
A |
1 |
A |
| Magnetic field
strength |
H |
Oe |
103/4 |
A/m |
1 |
A/m |
| Magnetization |
M, I |
emu/cm3 |
103 |
Wb/m2 |
1/0 |
A/m, J/(T m3) |
| Mass magnetization |
 |
emu/g |
1 |
(Wbm)/kg |
1/0 |
Am2/kgJ/(Tkg) |
| Magnetic moment |
m |
emu |
10-3 |
Wbm |
1/0 |
Am2, J/T |
| Susceptibility |
 |
—, (emu/(cm3Oe)) |
4 |
H/m a |
1/0 |
— b |
| Permeability of
vacuum |
0 |
1 |
4 × 10-7 |
H/m |
1 |
H/m |
| Permeability |
|
— |
4 × 10-7 = 0 |
H/m |
1 |
H/m |
| Demagnetizing factor |
N |
— c |
1/4 |
— d |
1 |
— e |
| Maximum
energy product |
(BH)max |
GOe |
10-1/4 |
J/m3 |
1 |
J/m3 |
| Energy density |
E, K |
erg/cm3 |
10-1 |
J/m3 |
1 |
J/m3 |
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a I = H. r defined by r = /0 is equal to in SI.
b M = H
c Nx + Ny + Nz = 4p
d Demagnetizing field: Hd = - (N / 0)I, Nx + Ny + Nz = 1
e Demagnetizing field: Hd = - N M, Nx + Ny + Nz = 1
Table 2 Conversion table for inch-unit quantities used in magnetic and optical recording.
| Quantity |
Inch-unit |
Conversion factor
to recommended unit |
Recommended unit f |
Notes |
| Linear recording density |
bpi, frpi, fci |
100/2.54 |
bit/m, fr/m, fc/m |
Use prefix as Mfr/m g |
| Areal recording density |
bit/in2 |
104 / 6.45 |
bit/m2 |
Use prefix as Tbit/m2 g |
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f These are not SI units.
g bit/mm, fr/mm and bit/mm2 are also used.
Table 3 Conversion table for quantities that should be expressed in SI.
| Quantity |
Unit |
Conversion factor
to recommended unit |
Recommended unit |
Notes |
| Length |
Å |
0.1 |
nm |
Temporary use in SI units |
| Pressure |
Torr, mmHg |
133.322 |
Pa |
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Others; The use of day (d), hour (h), and minute (min) along with "s" in SI, and of plane angles of degree ( ° ), minute ( ´ ), and second ( " ) along with "rad" in SI is authorized internationally, and therefore there is no need to take the trouble to convert them into SI. |
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