Glossary of Magnet Terms

Air Gap:

Air gap refers to the distance between a magnet’s poles via a nonmagnetic medium, often air.

Alnico Magnets:

Magnets made primarily with aluminum, nickel, cobalt, copper, iron and occasionally titanium. They can be cast or sintered and are very temperature stable. They are very hard and brittle, and do not lend themselves to conventional machining.

Anisotropic (oriented):

A preferred direction of magnetic orientation assigned during the magnetization process. Once the direction is determined, it cannot be changed.

Axially magnetized:

The term axially magnetized describes a magnet that is magnetized between two flat parallel surfaces.

BIH Curve:

The B/H curve compares the applied magnetic field (H) to the resulting flux density (B). The BH curve describes the properties of all magnetic materials.

BHmax Maximum Energy Product (Unit: MGOe Mega Gauss Oersted):

The BHmax represents the strongest point on the B/H Curve. When discussing the grade of a neodymium magnet, this number is frequently referred to as the “N” number, such as Grade N38 magnets.

Brmax (Residual Induction):

Brmax (also known as “Residual Flux Density”) refers to the amount of magnetic induction that remains in a saturated material after the magnetizing field is removed. This is the point when the hysteresis loop crosses the B axis with zero magnetizing force, indicating the maximum flux output from the specific magnet material.

C.G.S.:

The abbreviation for the “Centimeter, Grams, Second” system of measurement.

Ceramic Magnets:

Composed of strontium carbonate and iron oxide. Ceramic magnets are less expensive than alnico and neodymium magnets, with a lower temperature threshold than alnico, but greater than neodymium. Lower grade ceramic magnets can be non-oriented.

Coercivity:

A measure of the “performance” of a permanent magnet. It describes the strength of the reverse magnetic field required to demagnetize a magnet after it has been magnetized.

Coercive Force HC (Unit: Oe Oersted):

It is the demagnetizing force required to reduce observed induction B to zero when the magnet has reached saturation.

Curie Temperature (Tc):

Curie temperature (Tc) refers to the temperature at which a magnet loses its magnetism.

Demagnetization:

When a magnet loses its external magnetic field. This can occur through physical stress or corrosion, heating the magnet beyond its maximum operating temperature or by exposing the material to a strong demagnetizing magnetic field.

Demagnetization Curve:

The demagnetization curve, located in the second quadrant of the hysteresis loop, describes magnetic behavior during use. It is sometimes referred to as the B-H curve.

Demagnetization Force:

A force that reverses the direction of magnetization. Shock, vibration, and temperature can all be demagnetizing forces.

Dimensions:

The physical size of a magnet including any plating or coating.

Dimensional Tolerance:

An allowance given as a permissible range in the nominal dimensions of a finished magnet. The purpose of a tolerance is to specify the allowed leeway for variations in manufacturing.

Electromagnet:

Electromagnets consist of a solenoid with an iron core, which has a magnetic field only during the time of current flow through the solenoid.

Ferrite Magnet:

Composed of iron oxide and strontium.

Ferromagnetic Material:

A material that either js a source of magnetic flux or a conductor of magnetic flux. Most ferromagnetic materials have some component of iron, nickel, or cobalt.

Ferrous Metal :

“Ferrous” is derived from the Latin word meaning “containing iron”. Ferrous metals are often magnetic, but not exclusively.

Flux:

Describing the flow of the magnetic field of an object or magnetically receptive object.

Gauss:

Gauss is a unit of flux density equal to 1 maxwell per square centimeter. Gauss is represented by the symbol (B). 10,000 gauss equals one tesla.

Gauss meter:

A gauss meter measures the instantaneous magnetic induction (B) in Gauss.

Gilbert:

A Gilbert is the unit of magnetomotive force.

Hard Magnets:

Permanent magnets.

Hysteresis Loop:

A hysteresis loop is a plot of magnetizing force vs resultant magnetization (B/H curve) of a material while it is magnetized to saturation, demagnetized, magnetized in the opposite direction, and then re-magnetized. With ongoing recycling, this figure will form a closed loop that completely explains the magnetic material’s properties.

Induction B (Unit:

Gauss):

Induction refers to the magnetic flux per unit area of a section normal to the flux direction.

Intrinsic Coercive Force. Hci (Unit: Oersted):

Measures a magnetic material’s resistance to demagnetization. It is equivalent to the demagnetizing force that reduces the intrinsic induction (Bi) in the material to zero following magnetization to saturation.

Irreversible Losses:

Irreversible loss refers to partial demagnetization of a magnet due to exposure to high or low temperatures, external fields, shock, vibration, or other reasons. These losses are only recovered through remagnetization.

Isotropic (non-oriented):

Material that has no preferred direction of magnetic orientation, which allows magnetization in any direction.

Keeper / Shunt:

A keeper or shunt is a soft iron piece that is briefly placed between the poles of a magnetic circuit to prevent demagnetization. Neodymium and other contemporary magnets typically do not require this.

Kilogauss:

One Kilogauss equals 1 ,OOO Gauss or Maxwells per square centimeter.

Magnet:

A label that applies to objects made of materials that create a magnetic field. Magnets have poles, at least one north pole and one south pole.

Magnetic Assembly:

A composition of magnetic and non-magnetic materials designed to focus or direct the magnetic flux which increases its strength.

Magnetic Circuit:

A magnetic circuit consists of all elements, including air gaps and non-magnetic materials that the magnetic flux from a magnet travels on, starting from the north pole of the magnet to the south pole.

Magnetic Field:

The region in space where a magnetic force can be detected. The magnetic field strength and direction can be measured.

Magnetic Field Strength H (Unit: Oersted):

Measures the ability of an electric current or magnetic body to create a magnetic field at a specific spot.

Magnetic Flux:

A measurable notion that describes the “flow” of magnetic fields.

Magnetic Flux Density (Unit: Gauss):

Magnetic flux density refers to the number of lines of flux per unit area. One line of flux per square centimeter is one Maxwell.

Magnetic Induction (B):

Magnetic induction (B) refers to the magnetic field created by a particular field strength (H) at a certain location. At each point within the substance, it is the vector sum of magnetic field strength and intrinsic induction. Magnetic induction is defined as the flux per unit area that is normal to the magnetic path direction.

Magnetic Line of Force:

Magnetic force lines are imaginary lines in a magnetic field that indicate the direction of the flux at each point.

Magnetic Poles:

The points in all magnets where their magnetic strength is concentrated. They are labeled north and south because suspended magnets orient along north-south planes. Like poles repel each other, opposite poles attract.

Magnetic Saturation:

The maximum amount of energy that can be absorbed by a magnetic material to fully “charge” a magnet.

Magnetism:

The force of attraction or repulsion between materials made of certain elements, such as iron, nickel, cobalt, and their alloys.

Magnetomotive Force F or mmf (Unit: Gilbert or Ampere turns):

The magnetic potential difference between two points that creates a magnetic field, similar to voltage in electrical circuits. It is typically formed when a current flows through a wire coil.

Material Grade:

The ranking by which magnetic strength is determined. As a general rule, a higher number equates to a stronger magnet. For example, neodymium magnets have grades from N35 to N52. Magnetic grade factors into application, cost, size, operating temperature, and more.

Maximum Energy Product BHmax (Unit: Mega Gauss Oersteds, MGO):

A quality index representing both saturation magnetization and coercivity of a permanent magnet. The higher the energy product of a magnet, the smaller it needs to be to perform a specific function. The maximal energy product (BHmax) represents the magnetic field strength at its peak. The field strength of a completely saturated magnetic substance.

Max Force:

The maximum strength of a magnet when attracted to .5″ steel. Also known as “pull force” or “pull strength”.

Maximum Operating Temperature (Tmax):

Also known as maximum service temperature, is the maximum temperature of exposure that a magnet can forego without experiencing significant long-term instability or flux losses.

Maxwell:

A unit of magnetic flux. One maxwell represents one line of magnetic flux.

Magnetization Curve:

The magnetization curve represents the first quadrant of the hysteresis loop (B/H) curve for magnetic materials.

Magnetizing force is the magnetomotive force per unit of magnet length.

MGOe:

MGOe (Mega (million) Gauss Oersteds) is a unit of measurement used to determine a material’s maximal energy product.

Neodymium (Nd-Fe-B):

One of the “rare earth magnets,” composed of neodymium, iron, boron, and transition metals. Despite their small size, these magnets are incredibly strong and are high energy. Neodymium magnets should be handled with particular care to avoid injury.

North Pole:

The magnetic pole that attracts the geographic South Pole, where flux comes from.

Oersted (Oe):

The Oersted (Oe) is a unit of magnetizing force. 1 Oersted = 79.58 Aim).

Orientation:

Orientation refers to the direction of magnetization in a substance.

Orientation Direction:

The preferred direction in which some magnets, called oriented or anisotropic magnets, should be magnetized. The “orientation direction”, also known as “easy axis” or “axis”, is the direction that achieves it’s maximum magnetism. Other magnets, called unoriented or isotropic magnets, can be magnetized in any direction.

Paramagnetic Materials:

Materials that are not attracted to magnetic fields (wood, plastic, aluminum, etc.) and have a permeability slightly greater than 1.

Permanent Magnet:

A magnet that retains its magnetic properties in the absence of an inducing field or current.

Permeance (P):

Permeance measures the ease with which flux moves through a material or space. It is determined by dividing magnetic flux by magnetomotive force. Permeance is the opposite of reluctance.

Permeability (p):

Permeability refers to the ratio of a material’s magnetic induction to its magnetizing force (B/H). It is a measure of a material’s magnetization in the presence of a magnetic field.

Plating/Coating:

The process of covering the magnetic material to help prevent corrosion of the iron-based materials. Neodymium magnets are plated or coated to prevent corrosion. The magnet’s iron will rust if it is not protected from the elements. Some of the coatings include zinc, nickel-copper-nickel, and epoxy.

Polarity:

A permanent magnet’s pplarity distinguishes between the North and South poles.

Pole:

A pole refers to a concentrated area of magnetic flux.

Pull Force:

Also known as “pull strength”. Pull force is the force necessary to remove a magnet from a flat steel plate employing force perpendicular to the surface, or the magnet’s holding capacity limit.

Rare Earth Magnets:

A term used to refer to a group of magnetic materials whose alloys consist of one or more of the Rare Earth elements. These materials are characterized by exceptionally strong magnetic properties. Neodymium (Nd-Fe-B) and samarium cobalt (SmCo) are the strongest permanent magnets available and have significantly higher performance than ferrite (ceramic) and alnico magnets.

Relative Permeability:

The ratio of permeability of a material to that of a vacuum. In the C.C.S. system, the permeability is equal to 1 in a vacuum by definition. The permeability of air is also for all practical purposes equal to 1 in the C.G.S. system.

Reluctance (R):

Reluctance (R) is a measurement of a material’s relative resistance to the passage of flux. It is determined by dividing magnetomotive force by magnetic flux. Reluctance is the inverse of permeance.

Remanence Bd:

Remanence (Bd) refers to the magnetic induction that remains in a circuit after removing an applied magnetizing force.

Residual Flux Density (Brmax):

The term “Residual Flux Density” (Brmax) refers to the amount of magnetic induction corresponding to zero magnetic force in a magnetic material after a full magnetization jn a closed circuit.

Residual Induction (Brmax):

Also known as “Residual Flux Density” and refers to the magnetic induction that persists in a saturated magnetic material after the magnetizing field is eliminated. This is the point when the hysteresis loop crosses the B axis with zero magnetizing force, indicating the maximum flux output from the specific magnet material.

Return Path:

A conduction element in a magnetic circuit which provides a low reluctance path for the magnetic flux.

Reversible Temperature Coefficient:

The reversible temperature coefficient measures the reversible changes in flux produced by temperature differences.

Samarium Cobalt (SmCo):

A type of rare earth magnet composed of samarium, cobalt and iron. These magnets have high resistance to demagnetization, good temperature stability and are high-energy.

Saturation:

Saturation occurs when an increase in magnetizing force causes no further rise in magnetic induction in a magnetic material.

Shear Force:

The force on a magnet when it is placed in a perpendicular position to the ground. A magnet’s shear force holding power is usually about half of its strength in a horizontal position.

Shunt / Keeper:

A shunt or keeper is a soft iron item placed between the poles of a magnetic circuit to prevent demagnetization. Neodymium and other contemporary magnets typically do not require this.

S.I.:

Abbreviation for “Systeme International”. It refers to the International Standard System of units and is also known as the MKS system.

South Pole:

The magnetic pole that attracts to the geographic North Pole where flux from the North Pole terminates.

Stabilization:

Stabilization involves subjecting a magnet or assembly to high temperatures or external magnetic fields to demagnetize it to a specific level. Once completed, the magnet will no longer degrade when exposed to that level of demagnetizing influence.

Surface Field (Surface Gauss):

A Gauss meter measures the magnetic field strength at a magnet’s surface.

Temperature Coefficient:

The temperature coefficient calculates the decrease in magnetic flux due to higher operating temperatures. Magnetic flux loss is recovered when the working temperature is reduced.

Tesla:

A unit of magnetic induction or flux density. A Tesla = 10,000 Gauss.

Weber:

The weber unit represents total magnetic flux and is commonly used in practice. It is the quantity of magnetic flux that, when connected to a single-turn electric circuit at a uniform rate over a one-second period, produces an electromotive force of one volt.

Weight:

The weight of a single magnet.