Glossary of Magnet Technical Terminology

A group of permanent magnet alloys primarily made from aluminum, nickel, cobalt, and iron. These materials are known for high remanence and excellent thermal stability, retaining magnetic performance in moderately corrosive environments and at elevated temperatures.

The cross‑sectional area of the magnet perpendicular to its central magnetic flux line, measured in square centimeters (sq. cm.) at a given location. In engineering design calculations, Am is typically defined at the magnet’s neutral section.

Describes a material whose magnetic properties differ depending on the direction of measurement or magnetization. Anisotropic magnets have a preferred “easy” magnetization axis, established during manufacturing through either geometric forming or magnetocrystalline alignment.

The average cross‑sectional area of the air gap region where functional magnetic interaction occurs, measured in square centimeters (sq. cm.) in a plane normal to the central flux line.

The American Society for Testing and Materials, an international organization that develops and publishes voluntary technical standards for materials, products, systems, and services.

A magnet magnetized between two flat, parallel end surfaces, with its north and south magnetic poles located on these opposing faces.

The magnetic field induced at a point by an applied magnetic field strength (H). It represents the vector sum of the applied field strength and the resulting intrinsic induction. Units: Gauss (C.G.S.) or Tesla (S.I.).

The magnetic induction remaining in a magnetic material after an applied saturating magnetic field Hs has been removed. Units: Gauss.

The ratio of remnant induction to demagnetizing field strength. This is equivalent to the permeance coefficient Pc, and is also referred to as the shear line, load line, or unit permeance.

The magnetic energy that a material can deliver to an external circuit when operating at a specific point on its demagnetization curve. Units: Megagauss‑Oersteds (MGOe).

The highest value of the product of Bd and Hd on the demagnetization curve. It serves as the key indicator of a magnetic material’s potential energy output.

The unique contribution of the magnetic material itself to the total magnetic induction (B). It is defined as the vector difference between the induction in the material and the induction that would exist in a vacuum under the same field strength (H). Formula: Bi = B − H (Note: Bi and B are in Gauss; H is in Oersteds. For SI conversion, 1 A/m = 0.01256 Oe).

The maximum achievable intrinsic induction in a given magnetic material under saturation conditions.

The magnetic induction present in a magnetized material after magnetization and subsequent stabilization for end‑use application. Units: Gauss.

The magnetic induction corresponding to the point of maximum energy product (BH)max. Units: Gauss. (See also: Ho).

The magnetic induction that remains in a magnetic material at zero applied magnetizing force, following saturation in a closed magnetic circuit. Units: Gauss.

A graphical representation showing the relationship between magnetic flux density (B) and applied magnetic field strength (H).

The Centimeter‑Gram‑Second system of units, a historical metric system widely used in magnetism.

A configuration in which the entire external magnetic flux path of a magnet is contained within high‑permeability materials, minimizing flux leakage and enabling efficient flux circulation from the North pole to the South pole.

The demagnetizing field strength required to reduce the residual induction Br of a previously saturated magnetic material to zero. Units: Oersteds.

The applied magnetic field required to reduce the normal magnetic induction (B) to zero.

A critical parameter representing a material’s inherent resistance to demagnetization. It is the field strength needed to reduce the intrinsic induction (Bi) to zero. Units: Oersteds.

The characteristic temperature above which a ferromagnetic alloy loses its spontaneous magnetization and ferromagnetic behavior due to structural changes at the atomic level.

The process by which the magnetic flux inside a magnet is reduced to a lower level or eliminated, commonly caused by high temperatures, external opposing magnetic fields, or open‑circuit operation.

The second quadrant of the major hysteresis loop, which characterizes the magnetic behavior and performance of a material under real‑world operating load conditions.

Any external or internal influence — including opposing magnetic fields, thermal shock, mechanical impact, or vibration — that acts to reduce the magnetization level of a magnetic material.

The mass of a material per unit volume, typically expressed in grams per cubic centimeter (g/cm³).

Materials with magnetic permeability slightly less than 1 (such as copper, silver, and gold) that produce a weak repulsive force when exposed to an external magnetic field.

Cylindrical magnets in which the direction of magnetization runs parallel to the diameter, rather than along the central axial length.

The ratio of a magnet’s magnetic length to its diameter (or equivalent diameter for non‑round shapes).

The allowable range of deviation from the nominal dimensions of a finished magnet, reflecting practical manufacturing limits.

Microscopic regions within a magnetic alloy where the magnetic moments of atoms are aligned uniformly, creating a single shared magnetic direction.

Circulating electrical currents induced within conductive materials when exposed to changing magnetic fields. These currents generate opposing magnetic forces and can result in unwanted thermal losses or be harnessed for magnetic damping.

A temporary magnet consisting of a solenoid wound around a ferromagnetic core; it generates a magnetic field only while electric current is applied.

The quantity of work per unit charge. Units: Volts.

A dimensionless ratio that accounts for flux leakage from the magnetic circuit. It is defined as the ratio between the magnetic flux at the magnet’s neutral section and the average flux in the air gap: F=(Bm​Am​)/(Bg​Ag​).

A dimensionless ratio that accounts for the apparent magnetic circuit reluctance, compensating for the treatment of H as a constant.

The magnetic potential difference that tends to produce a magnetic field. Units: Gilberts (C.G.S.) or Ampere Turns (S.I.).

A class of magnetic materials (e.g., ferrites) that display high permeability and hysteresis but typically possess lower saturation induction than ferromagnetic materials.

A ferrimagnetic material, usually a composite of barium or strontium and iron oxide, manufactured through sintering or bonding.

Materials with high spontaneous magnetization and permeability significantly greater than 1 (e.g., iron, nickel, cobalt).

A measurable concept describing the total magnetic field “flow.” Units: Maxwells (C.G.S.) or Webers (S.I.).

The concentration of magnetic flux per unit area. Units: Gauss (C.G.S.) or Tesla (S.I.).

An electronic integrator used with a search coil to measure total magnetic flux.

Leakage flux associated with edge effects in a magnetic circuit.

An instrument used to measure instantaneous magnetic induction (B) at a specific point.

The C.G.S. unit of Magnetomotive Force (MMF).

The measure of the vector quantity that determines the ability of a body or current to induce a magnetic field. Units: Oersteds.

See Coercive Force.

The value of H on the demagnetization curve corresponding to Bd​. Units: Oersteds.

The value of H corresponding to the recoil induction Bm​. Units: Oersteds.

The magnetic field strength at the point of maximum energy product (BH)max​. Units: Oersteds. (Cross-reference: Bo).

A magnetic field where the lines of force are uniform, resulting in an equal field strength in all positions within the specified area.

The magnetizing force required to saturate a specific material. Units: Oersteds.

A closed curve obtained by plotting magnetic induction (B) against magnetizing force (H) as a material is cycled through saturation and reverse saturation.

The International Electrotechnical Commission, an international organization that develops and publishes standards for electrical, electronic, and related technologies.

Refer to the definition of Magnetic Induction, which is the magnetic field induced by a field strength (H) at a given point, representing the vector sum of the magnetic field strength and the resultant intrinsic induction.

A key characteristic of magnetic materials, referring to their inherent ability to resist permanent demagnetization caused by external factors such as opposing magnetic fields or high temperatures.

Refer to the definition of Bi, which is the specific contribution of the magnetic material to the total magnetic induction (B), defined as the vector difference between the induction in the material and the induction in a vacuum under the same field strength (H).

Partial demagnetization of a magnetic material caused by external influences including extreme temperatures, mechanical shock, or opposing magnetic fields. These losses cannot be reversed by restoring the material to its original conditions and require remagnetization to recover the original magnetic performance.

Describing a magnetic material that has uniform magnetic properties in all directions, with no preferred or “easy” axis of magnetization. Such materials can be magnetized effectively in any direction during application.

A component made of high-permeability material, usually mild steel, that is placed between the poles of a magnet. Its primary function is to reduce the reluctance of the air gap, protect magnets—especially AlNiCo magnets—from demagnetizing influences, and maintain the magnet’s flux over time.

A critical point on the B−H demagnetization curve where the curve deviates from linearity. If the magnet’s operating point falls below this knee, the magnetic induction (B) will change rapidly even with small variations in magnetic field strength (H), and the magnet will be unable to recover its original flux density. For example, Alnico 5 magnets exhibit a distinct knee at room temperature.

Refer to the definition of F, a dimensionless ratio that accounts for magnetic flux leakage in a magnetic circuit. It is calculated as the ratio of the magnetic flux at the magnet’s neutral section to the average flux in the air gap: F=(Bm·Am)/(Bg·Ag)

Magnetic flux that does not follow the intended or useful path of the magnetic circuit. Instead, it escapes to the surrounding environment, resulting in reduced efficiency of the magnetic system.

The length of the path traveled by the central magnetic flux line across the air gap in a magnetic circuit, measured in centimeters.

The total length of the magnet material that the central flux line passes through along the centerline of the magnetic circuit.

Refer to the definition of Dimension Ratio, which is the ratio of the magnet’s length (lm) to its diameter (or equivalent diameter for non-cylindrical magnets).

A straight line drawn from the origin of the demagnetization curve with a slope equal to the ratio of magnetic induction (B) to magnetic field strength (H). The point where this line intersects the demagnetization curve represents the actual operating point of the magnet in a specific application.

A functional assembly composed of magnetic and non-magnetic materials, often incorporating steel components to conduct and concentrate magnetic flux to a specific workface, thereby enhancing the performance of the magnetic system.

The direction in which the magnetic domains of an anisotropic magnet are aligned during manufacturing, which serves as the material’s preferred axis of magnetization.

An integrated system consisting of magnets, flux-conducting elements (such as steel), air gaps, and potentially electrical currents, designed to form a closed path for magnetic flux to flow efficiently.

A physical quantity that describes the torque a magnet experiences when placed in an external magnetic field. It is calculated using the formula: m=Br·V/μ₀, where Br is the Residual Flux Density in Tesla, V is the volume of the magnet in cubic meters, and μ₀ is the permeability of a vacuum.

Refer to the definition of H, a vector quantity that measures the ability of a body or electric current to induce a magnetic field, with units of Oersteds (C.G.S.) or Amperes per meter (S.I.).

Refer to the definition of B, the magnetic field induced at a given point by an applied magnetic field strength (H), representing the vector sum of the magnetic field strength and the resultant intrinsic induction. Its units are Gauss (C.G.S.) or Tesla (S.I.).

The physical length of a magnet measured along the direction of its magnetization, which directly affects the magnet’s magnetic performance and flux output.

Imaginary lines used to visually represent the direction and intensity of a magnetic field. At any point along these lines, the tangent indicates the direction of the magnetic flux.

The region on a magnet where magnetic flux lines are most concentrated, typically referred to as the North pole (where flux exits) and the South pole (where flux enters).

The process by which a material is subjected to an external magnetic field, causing its magnetic domains to align and thereby producing an external magnetic field.

A state in which a material retains the ability to exert an external magnetic field after being exposed to an external magnetizing force, resulting from the alignment of its magnetic domains.

The magnetomotive force per unit length of the magnet, which determines the extent to which the material can be magnetized. It is a key parameter in controlling the magnetization process.

Refer to the definition of F, the magnetic potential difference that drives the flow of magnetic flux in a magnetic circuit, with units of Gilberts (C.G.S.) or Ampere Turns (S.I.).

A closed curve obtained by plotting magnetic induction (B) against magnetic field strength (H) as a magnetic material is cycled between positive and negative saturation. This loop fully characterizes the material’s magnetic hysteresis properties.

A classification system used to identify the magnetic properties of a material, with specific grades indicating key parameters such as maximum energy product. For example, N42 is a common grade for Neodymium magnets, indicating a maximum energy product of approximately 42 MGOe.

Refer to the definition of (BH)max, the peak product of magnetic induction (Bd) and demagnetizing force (Hd) on the demagnetization curve, which serves as the primary metric for evaluating a magnet material’s potential energy output.

The highest temperature at which a magnet can be used continuously without experiencing significant long-term magnetic instability, irreversible losses, or structural damage. Exceeding this temperature may permanently degrade the magnet’s performance.

A high-energy rare-earth material (Nd2Fe14B). Due to its high iron content, NdFeB is highly susceptible to corrosion and rust if not properly sealed from the environment.

The plane passing through a magnet perpendicular to its central flux line at the point of maximum flux.

The “north-seeking” pole of a magnet which, when freely suspended, points toward the Earth’s magnetic North.

The C.G.S. unit for magnetic field strength (H).

A condition where a magnet has no external flux path of high-permeability material.

A straight line through the origin of the demagnetization curve with a slope of -Bd/Hd.

The specific point on the demagnetization curve where the magnet functions, defined by the intersection of the load line and the curve.

The “easy axis” along which an anisotropic magnet must be magnetized to achieve its specified properties.

Materials with a permeability slightly greater than 1 (e.g., aluminum, platinum) that are weakly attracted to magnetic fields.

A material that retains its magnetic properties after the external magnetizing field is removed.

The ratio of magnetic induction to magnetizing force (B/H).

The constant for B/H in a vacuum (4π×10^⁻⁷ H/m).

An industrial instrument used to measure the magnetic characteristics of material specimens.

The reciprocal of reluctance; a measure of the ease with which flux passes through a material.

A dimensionless value representing the “operating slope” of a magnet, determined by geometry and its magnetic environment.

Essential protective layers (e.g., Nickel-Copper-Nickel, Gold, Epoxy, Rubber) applied to Neodymium magnets to seal the iron component against corrosion and environmental degradation.

The property that differentiates the North pole from the South pole.

See Magnetic Pole.

Ferromagnetic materials used to shape, concentrate, or redirect lines of flux.

The force required to separate a magnet from a flat steel plate under perpendicular force.

A graphical plot of pull strength versus an increasing range of air gaps.

High-energy magnets utilizing lanthanide elements, primarily NdFeB and SmCo.

Induction remaining in a material after conditioning for final use.

The average slope of the recoil hysteresis loop.

The ratio of a material’s permeability to the permeability of a vacuum.

The resistance of a magnetic circuit to the passage of flux (R=F/ø).

The induction remaining in a magnetic circuit after the removal of the applied field.

See Remanence.

The maximum flux output from a material at zero air gap.

See Br.

Conduction elements in a circuit that provide a low-reluctance path for magnetic flux.

A rare-earth material characterized by high magnetic energy and superior performance at elevated temperatures.

The state in which all elementary magnetic moments are aligned, such that further increases in the applied field result in no additional increase in intrinsic induction.

A coil of wire used with a flux meter to measure changes in flux linkage within a field.

A high-permeability component used to divert flux or protect a magnet from demagnetization; synonymous with a keeper.

The standard metric system of units (Meter, Kilogram, Second).

A material manufactured by compacting powder and subjecting it to heat treatment to achieve full density and magnetic orientation.

Materials that are easily magnetized and demagnetized, typically used for flux conduction.

The pole of a magnet attracted to the Earth’s South Pole.

The process of exposing a magnet to demagnetizing influences (heat or opposing fields) to prevent future irreversible losses during operation.

The process of combining magnets to increase net pull strength.

The magnetic field strength at the surface of the magnet pole, as measured by a Gauss meter.

See Curie Temperature

A value describing the reversible percentage change in a magnetic property per unit of temperature. For remanence (Br), the logic is: Br(%) = [Br(T₁) − Br(T₂)] / [Br(T₁) ⋅ (T₂ − T₁)] × 100%. Note: A similar expression and logic apply to coercivity (HcB and Hci).

The S.I. unit for magnetic induction. 1 Tesla = 10,000 Gauss.

The S.I. unit for total magnetic flux. 1 Weber = 10^⁸ Maxwells.