Quantity | Symbol | SI Units | emu Units |
Magnetic field | H | A m-1 | Oe (oersted) |
Magnetic induction | B | T (tesla) | G (gauss) |
Magnetization | M | A m-1 | emu cm-3 |
Spontaneous magnetization | Ms | A m-1 | emu cm-3 |
Saturation magnetization | M0 | A m-1 | emu cm-3 |
Magnetic flux | Φ | Wb (weber) | maxwell |
Magnetic moment | m, µ | A m2 | erg/G |
Coercive field | Hc | A m-1 | Oe |
Remanence | Br | T | G |
Saturation magnetic polarization | Js | T | G |
Magnetic susceptibility | χ | ||
Magnetic permeability | µ | H m–1 (henry/meter) | |
Magnetic permeability of free space | µ0 | H m–1 | |
Saturation magnetostriction | λ (∆l/l) | ||
Curie temperature | TC | K | K |
Néel temperature | TN | K | K |
Magnetic moment µ = γħJ = g µB J
where
Earth’s magnetic field H = 56 A m–1 = 0.7 Oe
For iron: M 0 = 1.7⋅106 A m–1; B r = 0.8⋅106 A m–1
1 Oe = (1000/4π) A m–1; 1 G = 10–4 T; 1 emu cm–3 = 103 A m–1
1 Maxwell = 10–8 Wb
µ0 = 4π·10–7 H m–1
FIGURE 1. Typical curve representing the dependence of magnetic induction B on magnetic field H for a ferromagnetic material. When H is first applied, B follows curve (a) as the favorably oriented magnetic domains grow. This curve flattens as saturation is approached. When H is then reduced, B follows curve (b), but retains a finite value (the remanence Br ) at H = 0. In order to demagnetize the material, a negative field –Hc (where Hc is called the coercive field or coercivity) must be applied. As H is further decreased and then increased to complete the cycle (curve c), a hysteresis loop is obtained. The area within this loop is a measure of the energy loss per cycle for a unit volume of the material.
FIGURE 2. Schematic curve illustrating the B vs. H dependence for hard and soft magnetic materials. Hard materials have a larger remanence and coercive field, and a correspondingly large hysteresis loss.
FIGURE 3. Molar susceptibility of the elements at room temperature (cgs units of 10–6 cm3/mol). Values are not available for Z = 9, 61, and 84–89; Fe, Co, and Ni (Z = 26–28) are ferromagnetic. Data taken from the table “Magnetic Susceptibility of the Elements and Inorganic Compounds” in Section 4.
Z | Element | n | S | L | J | Gr. state | pcalc | pcalcb | pmeas |
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22 | Ti+3 | 1 | 1/2 | 2 | 3/2 | 2D3/2 | 1.73a | 1.55 | 1.8 |
23 | V+4 | 1 | 1/2 | 2 | 3/2 | 2D3/2 | 1.73a | 1.55 | 1.8 |
23 | V+3 | 2 | 1 | 3 | 2 | 3F2 | 2.83a | 1.63 | 2.8 |
23 | V+2 | 3 | 3/2 | 3 | 3/2 | 4F3/2 | 3.87a | 0.77 | 3.8 |
24 | Cr+3 | 3 | 3/2 | 3 | 3/2 | 4F3/2 | 3.87a | 0.77 | 3.7 |
25 | Mn+4 | 3 | 3/2 | 3 | 3/2 | 4F3/2 | 3.87a | 0.77 | 4.0 |
24 | Cr+2 | 4 | 2 | 2 | 0 | 5D0 | 4.90a | 0 | 4.9 |
25 | Mn+3 | 4 | 2 | 2 | 0 | 5D0 | 4.90a | 0 | 5.0 |
25 | Mn+2 | 5 | 5/2 | 0 | 5/2 | 6S5/2 | 5.92a | 5.92 | 5.9 |
26 | Fe+3 | 5 | 5/2 | 0 | 5/2 | 6S5/2 | 5.92a | 5.92 | 5.9 |
26 | Fe+2 | 6 | 2 | 2 | 4 | 5D4 | 4.90a | 6.70 | 5.4 |
27 | Co+2 | 7 | 3/2 | 3 | 9/2 | 4F9/2 | 3.87a | 6.54 | 4.8 |
28 | Ni+2 | 8 | 1 | 3 | 4 | 3F4 | 2.83a | 5.59 | 3.2 |
29 | Cu+2 | 9 | 1/2 | 2 | 5/2 | 2D5/2 | 1.73a | 3.55 | 1.9 |
58 | Ce+3 | 1 | 1/2 | 3 | 5/2 | 2F5/2 | 2.54c | 2.4 | |
59 | Pr+3 | 2 | 1 | 5 | 4 | 3H4 | 3.58c | 3.5 | |
60 | Nd+3 | 3 | 3/2 | 6 | 9/2 | 4I9/2 | 3.62c | 3.5 | |
61 | Pm+3 | 4 | 2 | 6 | 4 | 5I4 | 2.68c | ||
62 | Sm+3 | 5 | 5/2 | 5 | 5/2 | 6H5/2 | 0.84c | 1.5 |
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