

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 
cgsGauss units
B = H + 4M) 
Conversion
factor to SI 
MKSA units
(EH cor.)
B = _{0} H + I 
Conversion
factor to SI 
SI
(EB cor.)
B = _{0} (H + M ) 
Magnetic flux
density 
B 
G 
10^{4} 
T, Wb/m^{2} 
1 
T, Wb/m^{2} 
Magnetic flux 

Mx 
10^{8} 
Wb 
1 
Wb 
Magnetomotive
force 
V _{m} 
Gb 
10/4 
A 
1 
A 
Magnetic field
strength 
H 
Oe 
10^{3}/4 
A/m 
1 
A/m 
Magnetization 
M, I 
emu/cm^{3} 
10^{3} 
Wb/m^{2} 
1/_{0} 
A/m, J/(Tm^{3}) 
Mass magnetization 

emu/g 
1 
(Wbm)/kg 
1/_{0} 
Am^{2}/kgJ/(Tkg) 
Magnetic moment 
m 
emu 
10^{3} 
Wbm 
1/_{0} 
Am^{2}, J/T 
Susceptibility 

—, (emu/(cm^{3}Oe)) 
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 
101/4 
J/m^{3} 
1 
J/m^{3} 
Energy density 
E, K 
erg/cm^{3} 
10^{1} 
J/m^{3} 
1 
J/m^{3} 

^{a} I = H. _{r} defined by r = /_{0} is equal to in SI.
^{b} M = H
^{c} N_{x} + N_{y} + N_{z} = 4p
^{d} Demagnetizing field: H_{d} =  (N / _{0})I, N_{x} + N_{y} + N_{z} = 1
^{e} Demagnetizing field: H_{d} =  N M, N_{x} + N_{y} + N_{z} = 1
Table 2 Conversion table for inchunit quantities used in magnetic and optical recording.
Quantity 
Inchunit 
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/in^{2} 
10^{4} / 6.45 
bit/m^{2} 
Use prefix as Tbit/m2 ^{g} 

^{f} These are not SI units.
^{g} bit/mm, fr/mm and bit/mm^{2} 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 


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. 
