Permanent Magnet Glossary Technical definitions for permanent magnet materials, magnetic measurements, design terminology, and industry specifications.
A–D
A
Air Gap
The non-magnetic space between magnetically coupled components in a magnetic circuit.
Alnico
Permanent magnet alloy primarily composed of aluminum, nickel, and cobalt.
Anisotropic Magnet
Magnet material processed with a preferred magnetic orientation for higher performance in one direction.
Axial Magnetization
Magnetized through thickness, with north and south poles on opposite flat faces.
B
B (Magnetic Induction)
Magnetic flux density within a material or magnetic circuit, commonly measured in gauss or tesla.
B-H Curve
Graph showing the relationship between magnetic induction (B) and applied magnetic field strength (H).
BHmax
Maximum energy product of a permanent magnet material, expressed in MGOe or kJ/m³.
Br (Remanence)
Residual magnetic induction remaining after magnetization.
C
Ceramic Magnet
Common name for ferrite permanent magnets.
Closed Circuit Testing
Method of measuring magnetic properties in a controlled magnetic path.
Coercivity (Hc)
Reverse magnetic field required to reduce magnetic induction to zero.
Curie Temperature (Tc)
Temperature where ferromagnetic properties are lost.
D
Demagnetization
Loss or reduction of magnet strength caused by heat, reverse fields, shock, or time.
Demagnetization Curve
Second quadrant of the B-H curve used for permanent magnet design.
Diametric Magnetization
Poles located on opposite curved sides of a cylindrical magnet.
Domain
Microscopic region in magnetic material with aligned magnetic moments.
E–H
E
Energy Product
Measure of usable magnetic energy available from a magnet.
Extrinsic Coercivity
Another reference to normal coercivity (Hc).
Eddy Currents
Circulating currents induced in conductive materials by changing magnetic fields.
Electromagnet
Magnet created by electric current flowing through a coil.
F
Ferrite Magnet
Ceramic permanent magnet material known for low cost and corrosion resistance.
Field Strength (H)
Magnetizing force, commonly measured in oersteds or A/m.
Flux
Total magnetic field passing through a given area.
Flux Density
Magnetic flux per unit area.
G
Gauss
CGS unit of magnetic flux density.
Grade
Performance classification of magnet materials such as N42 or N52.
Grain Orientation
Alignment of crystal structure to improve magnetic performance.
Green Strength
Mechanical strength of compacted powder before sintering.
H
Hall Effect Sensor
Electronic device used to detect magnetic fields and position changes.
Hc
Symbol for coercive force.
Hci (Intrinsic Coercivity)
Resistance to irreversible demagnetization.
Hysteresis
Lag between applied field and magnetic response.
I–L
I
Intrinsic Coercivity
Reverse field required to reduce intrinsic induction to zero.
Injection Molded Magnet
Bonded magnet produced by thermoplastic injection molding.
Isotropic Magnet
Magnet material with no preferred orientation.
Induction
Another term for magnetic flux density (B).
K
kA/m
Kiloamps per meter, SI unit for magnetic field strength.
kG
Kilogauss, equal to 1,000 gauss.
kJ/m³
SI unit for magnetic energy product.
Keeper
Steel bar used to preserve magnetization in some magnet systems.
L
Load Line
Line representing operating conditions of a magnet in a magnetic circuit.
Leakage Flux
Magnetic flux not contained in the intended path.
Linear Motor Magnet
Magnet used in linear motion motor systems.
Lamination
Thin steel layers used to reduce eddy current losses.
M–P
M
Magnetic Circuit
Path followed by magnetic flux.
Magnetic Pole
Region where magnetic field emerges or enters a magnet.
MGOe
Mega Gauss Oersteds, common unit for energy product.
Multi-Pole Magnetization
Alternating north/south poles across one magnet surface.
N
NdFeB
Neodymium-Iron-Boron magnet material.
Neodymium Magnet
High-strength rare earth permanent magnet.
Normal Coercivity
Reverse field needed to reduce B to zero.
North Pole
One magnetic end of a magnet.
O
Open Circuit Condition
Magnet operating without a completed magnetic path.
Oersted (Oe)
CGS unit of magnetic field strength.
Orientation
Direction in which magnetic domains are aligned during manufacturing.
Operating Point
Actual working point of a magnet on its demagnetization curve.
P
Permeability
Ability of a material to support magnetic flux.
Permeance Coefficient (Pc)
Ratio based on magnet geometry and circuit conditions affecting operating point.
Permanent Magnet
Material retaining magnetization without external power.
Pull Force
Maximum force required to separate a magnet from steel under ideal conditions.
R–T
R
Radial Magnetization
Magnetized inward/outward across the radius.
Rare Earth Magnet
High-performance magnet using rare earth materials.
Recoil Permeability
Slope of minor hysteresis loop after partial demagnetization.
Remanence
Residual induction after removal of magnetizing force.
S
Samarium Cobalt (SmCo)
Rare earth magnet with strong temperature resistance.
Saturation
Condition where increasing field produces little additional magnetization.
Sintered Magnet
Powder compacted and heat fused into solid form.
South Pole
Opposite magnetic pole from north.
T
Tesla (T)
SI unit of magnetic flux density. 1 T = 10,000 gauss.
Temperature Coefficient
Rate magnetic properties change with temperature.
Tolerance
Permitted dimensional variation.
Torque Magnet
Magnet used in rotary motion systems.