Magnetic Susceptibilities of Paramagnetic and Diamagnetic Materials at 20°C

Material
χm=Km-1
(x 10-5)
Paramagnetic
Iron oxide (FeO)
720
Iron amonium alum
66
Uranium
40
Platinum
26
Tungsten
6.8
Cesium
5.1
Aluminum
2.2
Lithium
1.4
Magnesium
1.2
Sodium
0.72
Oxygen gas
0.19
Diamagnetic
Ammonia
-.26
Bismuth
-16.6
Mercury
-2.9
Silver
-2.6
Carbon (diamond)
-2.1
Carbon (graphite)
-1.6
Lead
-1.8
Sodium chloride
-1.4
Copper
-1.0
Water
-0.91
ParamagnetismDiamagnetism
 Here the quantity Km is called the relative permeability, a quantity which measures the ratio of the internal magnetization to the applied magnetic field. If the material does not respond to the magnetic field by magnetizing, then the field in the material will be just the applied field and the relative permeability Km =1. A positive relative permeability greater than 1 implies that the material magnetizes in response to the applied magnetic field. The quantity χm is called magnetic susceptibility, and it is just the permeability minus 1. The magnetic susceptibility is then zero if the material does not respond with any magnetization. So both quantities give the same information, and both are dimensionless quantities.

For ordinary solids and liquids at room temperature, the relative permeability Km is typically in the range 1.00001 to 1.003. We recognize this weak magnetic character of common materials by the saying "they are not magnetic", which recognizes their great contrast to the magnetic response of ferromagnetic materials. More precisely, they are either paramagnetic or diamagnetic, but that represents a very small magnetic response compared to ferromagnets.

The gases N2 and H2 are weakly diamagnetic with susceptabilities -0.0005 x 10-5 for N2 and -0.00021 x 10-5 for H2. That is in contrast to the large paramagnetic susceptability of O2 in the table.

 Index

Tables

Reference
Young
Section 29-8
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Magnetic Properties of Ferromagnetic Materials

Material
Treatment
Initial Relative
Permeability
Maximum Relative
Permeability
Coercive
Force
(oersteds)
Remanent Flux
Density
(gauss)
Iron, 99.8% pure
Annealed
150
5000
1.0
13,000
Iron, 99.95% pure
Annealed in hydrogen
10,000
200,000
0.05
13,000
78 Permalloy
Annealed, quenched
8,000
100,000
.05
7,000
Superpermalloy
Annealed in hydrogen, controlled cooling
100,000
1,000,000
0.002
7,000
Cobalt, 99% pure
Annealed
70
250
10
5,000
Nickel, 99% pure
Annealed
110
600
0.7
4,000
Steel, 0.9% C
Quenched
50
100
70
10,300
Steel, 30% Co
Quenched
...
...
240
9,500
Alnico 5
Cooled in magnetic field
4
...
575
12,500
Silmanal
Baked
...
...
6,000
550
Iron, fine powder
Pressed
...
...
470
6,000

In this table the remanent flux density is the retained magnetic field B, and the SI unit for B is the Tesla (T). 1 Tesla = 10,000 gauss. The "coercive force" is the applied reverse magnetic field strength H required to force the net magnetic field back to zero after magnetization. The SI unit for H is A/m, and 1 A/m = 0.01257 oersteds.

Discussion of relative permeability
Coercivity and Remanence
 Index

Tables

Reference
Brown
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