1. Fundamentals of Permanent Magnets
Alliance LLC

2. Magnetic Orientation Isotropic Anisotropic (non-oriented) (oriented)
Magnetic strength is the
same in all directions
Can be magnetized in any
direction
Almost all bonded magnets
Magnetic strength is greatest
in the oriented direction
Can be magnetized only in
the oriented direction
Almost all sintered magnets
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3. Main Magnetic Properties
Residual induction - Br
Coercive force - Hc
Intrinsic coercive force - Hci
Maximum Energy Density – (BH)max
Maximum Working Temperature - Tw
Reversible Temperature Coefficient - -%Br/C
Curie Temperature - Tc
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4. Main Types of Magnet Materials
Alnico
Ferrite
Samarium Cobalt
Neodymium Iron Boron
Bonded Grades of the Above Types
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5. Typical Supplier Data Sheet
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6. Hysteresis / Demagnetization Curve
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7. +B I
Br, Bi I
(BiH)max
Hci Hc -H +H -B
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8. Temperature Effects
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9. Alnico Ferrite SmCo NdFeB(SH)
15.0
13.5
12.0
10.5
9.00
7.50
6.00
4.50
3.00
1.50
B (Kg)
H (KOe)
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10. Magnet Characteristics
Materials
Typical Shapes
Pro
Con
Cast Alnico
AlNiCo
Rods, Bars, U shape
and other cast type
High Br
High working T
Good T coef.
Very Low Hc
High cost
High L/D
Requires Cast
Sintered Alnico
Powder pressed to shape
Complex shapes
High Br, T
Requires Tool
Low market
Ceramic/Ferrite
SrFe2O3
Blocks, Rings, Arcs, Discs
Most flux for $
High usage
Low corrosion
Low Br
Requires tool
Simple shapes
Samarium
Cobalt
SmCo
Blocks, Rings, Discs
Arcs, Segments
No corrosion
Very low T coef
Stable, No tool
Very expensive
High Co content
Neodymium
NdFeB
Highest magnetic properties
No tooling
Corrodes
Low working T
Difficult to Mag
Bonded Grades
All materials
Difficult geometries
Can be insert molded
or over-molded
Various resins
High tooling
Low magnetics
High volumes
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11. Cast Alnico Magnets
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12. Ferrites / Ceramics (SrFe2O3)
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13. Neodymium, Neo, NdFeB
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14. Injection and Compression Molded
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