Air Gap
The distance between one pole of the magnet and the other
magnetic material. The air gap is non-magnetic, usually air, but
can be a non-magnetic material.
Maximum Energy Product (BHmax)
The maximum energy product on the point of the B/H curve that
has the highest strength. This is reflected as mgo, or mega gauss
oersteds. This maximum strength is how the material
grade is determined, i.e. N35, N42, N48, etc.
Materials that have an orientation that is aligned in a preferred
direction. Anisotropic magnets have their alignment defined
during the manufacturing process in a strong magnetic field.
Once the preferred direction, this direction cannot be changed.
The unit of magnetic flux in the centimeter-gram-second (cgs)
system. One Maxwell is one line of magnetic flux.
B/H Curve
The curve produced from plotting the value B (induction) against
H (applied magnetic field). The curve will describe the qualities of
the magnetic material
Mega (million) gauss oersteds is a unit of measurement typically
used in stating the maximum energy product for a given material.
BHmax (Maximum Energy Product)
The maximum energy product not he point of the B/H curve
that the highest strength. This is reflected as mgo, or mega gauss
oersteds. This maximum strength is how the material grade is
determined, i.e. N35, N42, N48, etc.
North Pole
The pole of a magnet which points to the north magnetic pole of
the earth. All magnets have a north and south pole.
This is also known as the Residual Flux Density, and is the point
on the hysteresis loop that crosses the B axis at zero magnetizing
force. Once the magnet is saturated, the magnetic field is removed
resulting in the maximum flux output of the magnet.
The centimeter-gram-second (C.G.S.) unit of magnetic field strength.
A abbreviation system of units utilizing centimeters, grams, and seconds.
Open Circuit
An open circuit exists when a magnet is by itself with no return flux path
due to high permeability material.
Coercive Force (Hc)
The resistance of a magnet to demagnetizing forces once an opposing
magnetic field is applied to remove the residual magnetism.
In an anisotropic magnet, the direction that the magnetic field flows.
Anisotropic magnets have their direction of orientation determined during the
manufacturing process and can only be magnetized in that specific direction.
Curie Temperature
The temperature at which a magnet loses all of its magnetic properties.
Permanent Magnet
A magnet that retains its magnetism even after it is removed from a magnetic
field. Unlike an electromagnet that requires current to achieve a magnetic field,
a permanent magnet remains "on" without the need for any outside field.
Demagnetization Curve
The second quadrant of the hysteresis loop, and also referred to as the
B/H Curve.Demagnetization Curves can be found on our materials page
Permeance Coefficient (Pc)
Also called that load-line, B/H or operating slope. Permeance coefficients can
be found as the line on the demagnetization curve where a given magnet
operates, and depends upon both the shape and surroundings of the magnet.
This number defines how hard it is for the field lines to go from the North Pole
to the South Pole of the magnet.
Demagnetization Force
A force that pushes the magnet to demagnetize slightly or completely.
These forces could include a magnetizing force in opposite direction,
shock, temperature, and vibration.
Plating and/or Coating
The protective coating on a magnet. Neodymium magnets require a coating
to protect from corrosion since their material make up is largely iron.
Depending upon the application and environment, the correct coating choice
is as important as the correct selection of the magnetic material.
Dimensional Tolerance
The total amount a dimension may vary between the upper and lower
limits. Tolerances are used to control the amount of variation in a
manufactured part.
The north and south pole of the magnet.
Ferromagnetic Material
Ferromagnetic materials can carry magnetic flux when against
a magnet, and is usually made of steel. These materials can
act like a magnet until the magnetic material is removed.
Pull Force
The force required to pull a magnet free from a flat steel plate using a force
perpendicular to the surface. This will determine the holding power of the magnet.
The magnetic entity which flows from one pole to the other in a
magnetic circuit.
A measure of the relative resistance of a material to the passage of flux, which is
calculated by dividing magneto motive force by magnetic flux.
Unit of magnetic induction, B. 10,000 gauss equals 1 Tesla
Return Path
Conduction elements in a magnetic circuit that provide a low reluctance path
for the magnetic flux.
Hysteresis Loop
The Full 4-quadrant graph showing the relationship of the
induction of a magnetic material to an applied magnetic field.
The first quadrant of the loop is the magnetization curve,
while the second quadrant of the loop is the Demagnetization Curve.
The condition of a magnet where an increase in magnetizing force produces
no further increase in the magnetic material. When this condition is met,
all of the magnetic moments have the same alignment. A magnet should
always be magnetized to saturation.
Induction (B)
The concentration of flux over a given area measured
in a gauss or Tesla.
A sintered magnet is compacted powder which is then heat treated to achieve
full density and orientation.
Intrinsic Coercive Force (Hci)
The resistance of a magnet material to demagnetization. It is equal to
the demagnetizing force which reduces the intrinsic induction, Bi, in the
material to zero after magnetizing to saturation.
South Pole
The pole of a magnet which points to the south magnetic pole of the earth.
All magnets have a north and south pole.
Irreversible Losses
Partial demagnetization of the magnet, caused by exposure
to high or low temperatures, external fields, shock, vibration,
or other factors. The losses are only recoverable by remagnetizing.
The process of exposing a fully saturated magnet or magnetic assembly to
an elevated temperature or external magnetic field to demagnetize it to a
predetermined level. Once stabilized through this process, the magnet should
not experience any future degradation when exposed to that level of
demagnetizing influence again, or better known as preventing irreversible
losses during.
Isotropic Material
A material that can be magnetized along any axis or direction lion.
Opposite of anisotropic magnets.
Surface Field
The magnetic field strength at the surface of the magnet as
measured by a gauss meter.
One kilogauss = 1,000 gauss
Temperature Coefficient
A factor that is used to calculate the decrease in magnetic flux with
an increase in operating temperature. This loss is recovered when
the operating temperature is decreased. Understanding temperature
requirements in an application will allow for the correct selection of
magnetic material.
Load Line
The line drawn from the origin of the demagnetization curve with the slope
of the B/H. The intersection represents the operating point of the magnet.
One (1) Telsa equals 10,000 gauss.
A piece of iron that has its component atoms oriented within the material that
the material exhibits properties of magnetism. This allows the material to attract
other materials containing iron, or align itself with an external magnetic field.
The practical unit of magnetic flux. It is the amount of the magnetic
flux which, when linked at a uniform rate with a single-turn electric
current during an interval of 1 second, will induce in this circuit an
electromotive of force of 1 volt.
Magnetic Assembly
A combination of magnetic and/or non-magnetic materials that includes the
permanent magnet to generate flux. This assembly of specific materials is
designed to provide a defined magnetic solution.
Magnetic Circuit
One or more closed loop paths containing magnetic flux. The magnetic circuit
is equivalent to an electrical circuit.
Material Grade
Magnet are graded according to strength, and as a rule, the higher the number,
the "stronger" the magnet. For example, neodymium magnets (NdFeB) have
grades from N35 to N55. The energy product of a magnet is specified in units of
gauss oersted. Choice of a magnetic grade for a specific application will require
consideration of magnetic field required, cost, size, operating temperature,
coatings and interaction with other materials.
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