Anisotropic Magnet: A magnet having a preferred direction of magnetic orientation, so that the magnetic characteristics are optimum in one preferred direction.

Closed Circuit: This exists when the flux path external to a permanent magnet is confined within high permeability materials that compose the magnet circuit.

Coercive Force, Hc: The demagnetizing force, measured in Oersteds, necessary to reduce observed induction, B, to zero after the magnet has previously been brought to saturation.

Curie Temperature, Tc: The temperature at which the parallel alignment of elementary magnetic moments completely disappears, and the material is no longer able to hold magnetization.

Demagnetization Curve: The second quadrant of the hysteresis loop, generally describing the behavior of magnetic characteristics in actual use. Also known as the B-H Curve.

Eddy Currents: Circulating electrical currents that are induced in electrically conductive elements when exposed to changing magnetic fields, creating an opposing force to the magnetic flux. Eddy currents can be harnessed to perform useful work (such as damping of movement), or may be unwanted consequences of certain designs, which should be accounted for or minimized.

Electromagnet: A magnet, consisting of a solenoid with an iron core, which has a magnetic field existing only during the time of current flow through the coil.

Energy Product: Indicates the energy that a magnetic material can supply to an external magnetic circuit when operating at any point on its demagnetization curve. Calculated as Bd x Hd, and measured in Mega Gauss Oersteds, MGOe.

Ferromagnetic Material: A material whose permeability is very much larger than 1 (from 60 to several thousand times 1), and which exhibits hysteresis phenomena.

Flux: The condition existing in a medium subjected to a magnetizing force. This quantity is characterized by the fact that an electromotive force is induced in a conductor surrounding the flux at any time the flux changes in magnitude. The cgs unit of flux is the Maxwell.

Fluxmeter: An instrument that measures the change of flux linkage with a search coil.

Fringing Fields: Leakage flux particularly associated with edge effects in a magnetic circuit.

Gauss: Lines of magnetic flux per square centimeter, cgs unit of flux density, equivalent to lines per square inch in the English system, and Webers per square meter or Tesla in the SI system.

Gaussmeter: An instrument that measures the instantaneous value of magnetic induction, B. Its principle of operation is usually based on one of the following: the Hall effect, nuclear magnetic resonance (NMR), or the rotating coil principle.

Hysteresis Loop: A closed curve obtained for a material by plotting corresponding values of magnetic induction, B, (on the abscissa) against magnetizing force, H, (on the ordinate).

Induction, B: The magnetic flux per unit area of a section normal to the direction of flux. Measured in Gauss, in the cgs system of units.

Intrinsic Coercive Force, Hci: Measured in Oersteds in the cgs system, this is a measure of the material's inherent ability to resist demagnetization. It is the demagnetization force corresponding to zero intrinsic induction in the magnetic material after saturation. Practical consequences of high Hci values are seen in greater temperature stability for a given class of material, and greater stability in dynamic operating conditions.

Intrinsic Induction, Bi: The contribution of the magnetic material to the total magnetic induction, B. It is the vector difference between the magnetic induction in the material and the magnetic induction that would exist in a vacuum under the same field strength, H. This relationship is expressed as: BI = B-H.

Irreversible Loss: Defined as the partial demagnetization of a magnet caused by external fields or other factors. These losses are only recoverable by re-magnetization. Magnets can be stabilized to prevent the variation of performance caused by irreversible losses.

Isotropic Magnet: A magnet material whose magnetic properties are the same in any direction, and which can therefore be magnetized in any direction without loss of magnetic characteristics.

Keeper: A piece of soft iron that is placed on or between the poles of a magnet, decreasing the reluctance of the air gap and thereby reducing the flux leakage from the magnet.

Knee of the Demagnetization Curve: The point at which the B-H curve ceases to be linear. All magnet materials, even if their second quadrant curves are straight line at room temperature, develop a knee at some temperature. Alnico 5 exhibits a knee at room temperature. If the operating point of a magnet falls below the knee, small changes in H produce large changes in B, and the magnet will not be able to recover its original flux output without re-magnetization.
Leakage Flux: That portion of the magnetic flux that is lost through leakage in the magnetic circuit due to saturation or air-gaps, and is therefore unable to be used.

Length of air-gap, Lg: The length of the path of the central flux line in the air-gap.

Load Line: A line drawn from the origin of the Demagnetization Curve with a slope of -B/H, the intersection of which with the B-H curve represents the operating point of the magnet. Also see Permeance Coefficient.
Magnetic Circuit: An assembly consisting of some or all of the following: permanent magnets, ferromagnetic conduction elements, air gaps, electrical currents.

Magnetic Flux: The total magnetic induction over a given area. When the magnetic induction, B, is uniformly distributed over an area A, Magnetic Flux = BA.

Magnetizing Force, H: The magnetomotive force per unit length at any point in a magnetic circuit. Measured in Oersteds in the cgs system.

Magnetomotive Force, F: Analogous to voltage in electrical circuits, this is the magnetic potential difference between any two points.

Maximum Energy Product, BHmax: The point on the Demagnetization Curve where the product of B and H is a maximum and the required volume of magnet material required to project a given energy into its surroundings is a minimum. Measured in Mega Gauss Oersteds, MGOe.
North Pole: That pole of a magnet which, when freely suspended, would point to the north magnetic pole of the earth. The definition of polarity can be a confusing issue, and it is often best to clarify by using "north seeking pole" instead of "north pole" in specifications.

North Pole: That magnetic pole which attracts the geographic North Pole.

Oersted, Oe: A cgs unit of measure used to describe magnetizing force. The English system equivalent is Ampere Turns per Inch, and the SI system's is Ampere Turns per Meter.

Orientation Direction: The direction in which an anisotropic magnet should be magnetized in order to achieve optimum magnetic properties. Also known as the "axis", "easy axis", or "angle of inclination".

Paramagnetic Material: A material having a permeability slightly greater than 1.

Permeance: The inverse of reluctance, analogous to conductance in electrical circuits.

Permeance Coefficient,Pc: Ratio of the magnetic induction, BD, to its self demagnetizing force, HD PC = BD / HD This is also known as the "load line", "slope of the operating line", or operating point of the magnet, and is useful in estimating the flux output of the magnet in various conditions. As a first order approximation, BD / HD = Lm/Lg, where Lm is the length of the magnet, and Lg is the length of an air gap that the magnet is subjected to. PC is therefore a function of the geometry of the magnetic circuit.

Pole Pieces: Ferromagnetic materials placed on magnetic poles used to shape and alter the effect of lines of flux.

Relative Permeability: The ratio of permeability of a medium to that of a vacuum. In the cgs 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 cgs system.

Reluctance, R: Analogous to resistance in an electrical circuit, reluctance is related to the magnetomotive force, F, and the magnetic flux by the equation R = F/(Magnetic Flux), paralleling Ohm's Law where F is the magnetomotive force (in cgs units).

Remanence, BD: The magnetic induction that remains in a magnetic circuit after the removal of an applied magnetizing force. If there is an air gap in the circuit, the remanence will be less than the residual induction, Br.

Residual Induction, Br: This is the point at which the hysteresis loop crosses the B axis at zero magnetizing force, and represents the maximum flux output from the given magnet material. By definition, this point occurs at zero air gap, and therefore cannot be seen in practical use of magnet materials.

Return Path: Conduction elements in a magnetic circuit which provide a low reluctance path for the magnetic flux.

Reversible Temperature Coefficient: A measure of the reversible changes in flux caused by temperature variations.

Saturation: The condition under which all elementary magnetic moments have become oriented in one direction. A ferromagnetic material is saturated when an increase in the applied magnetizing force produces no increase in induction. Saturation flux densities for steels are in the range of 16,000 to 20,000 Gauss.

Search Coil: A coil conductor, usually of known area and number of turns that is used with a fluxmeter to measure the change of flux linkage with the coil.

Stabilization: Exposure of a magnet to demagnetizing influences expected to be encountered in use in order to prevent irreversible losses during actual operation. Demagnetizing influences can be caused by high or low temperatures, or by external magnetic fields.

Temperature Coefficient: A factor, which describes the change in a magnetic property with change in temperature. Expressed as percent change per unit of temperature.

Weber: The practical unit of magnetic flux. It is the amount of magnetic flux which, when linked at a uniform rate with a single-turn electric circuit during an interval of 1 second, will induce in this circuit an electromotive force of 1 volt.

Inspection standard for permanent magnet

1) When the permanent magnet is not supplied with specific size and shape, the properties of material should be tested. The test standard is as per GB/T3217-95permanent magnet (hard magnet) material test trial method,GJB2453-95rare earth permanent magnet material general criterion and relevant enterprise standard. GB/T3217 stipulated the test method. Enterprise standard stipulated the test process and sampling method.

2)When the permanent magnet is supplied with specific size and shape, the properties of the magnetic component should be tested. The properties of the material are only tested for reference.

3) For different permanent magnetic components, the test parameters and test methods are different. For magnetic ring, the test parameter is diametric flux density. For magnetic segment and block, the parameters can be surface field, magnetic flux etc. The magnetic flux is better.

A digital tesla meter can test diametric flux density

With a transverse sensor. Magnetic flux can be tested by permanent magnet tesla meter and Helmholtz coil.

For more information about the international standard, you may

turn to the following reference:

IEC 404-5(1982) magnetic material Part 5:test measure for hard magnet(permanent magnet) material properties.

JISC 2501-1989 Test method for magnetic material(Japan)

4) When the permanent magnet is supplied as magnetic assembly or component,the properties of the magnetic assembly or component should be tested. The buyer and seller will negotiate and decide the specific test method with each other.

5) Unless specified by the user, we will adopt standard sampling method for the final test of the permanent magnet.

Purchasing Guide

1) Permanent magnetic component is not a standard mechanical component , but a functional component. It is generally produced as per the customer's demand. So a certain process period is involved. The lead time is about 10-15 days.

2) In order to meet the urgent need, we keep the following rough semi-finished products in stock. You may choose among them according to your design requirement to save the production time.

3)The maximum dimension of the magnet is 60mm,the maximum dimension in magnetization direction is 200mm;the minimum dimension of the magnet is 2mm. For small size, the waste during production is more, so the cost per unit weight is high. Preferential size of the produc:

4) The products will be tested strictly as per relevant standard. Unless specified by the user, the discrepancy of the properties of the product is below 5%.For quality problem found by the user, please give reasons and return the products to us.

6) Shipment method: express air mail, transit time 2~4days,EMS,transit time3~7days.express transportation by train,transit time5~10days normal mail service Normal transportation by train. The specific shipment method is decided by the order quantity and the price.

Permanent magnet supply direction

1) Permanent magnet supplied under two conditions,Magnetized or no magnetized, is usually not marked its polarity. If the user require, we could mark the polarity by the means agreed on. When pacing the order, the user should inform the supply condition and if the mark of the polarity is necessary.

2) The magnetization field of permanent magnet is related to the permanent magnetic material type and its intrinsic coercive force. If the magnet need magnetization and demagnetization, please contact with us and ask for technique support.

There are two methods to magnetize the magnet: DC field and pulse magnetic field.

There are three methods to demagnetize the magnet:demagnetization by heat is a special process technique.demagnetization in AC field. Demagnetization in DC field. This asks for very strong magnetic field and high demagnetization skill.

3) geometry shape and magnetization direction of permanent magnet: in principle, we produce permanent magnet in various shapes. Usually, it includes block, disc, ring, segment etc.

4) Size and tolerance of the permanent magnet: Except for the dimension in the direction of magnetization, the maximum dimension of the permanent magnet is not exceed 60mm, which is limited by the orientation field and sintering equipment. The dimension in the magnetization direction is up to 200mm.

Usually the permanent magnet should be ground. The tolerance after grinding is usually +/-0.05. Tolerance +/-0.02mm is available too, but the cost will be higher.

We suggest the user to refer to our national military standard GJB2453rare earth permanent magnet general criterion in the design of the tolerance of the permanent magnet.

Surface protection and surface coating for the permanent magnet

1) Surface protection: Under the normal atmospheric condition(room temp. humidity 50%),it is unnecessary for special surface protection to the permanent magnet. However, for many applications, the surface protection is a must. This is for the following reasons:

Anticorruption protection: The rare earth permanent magnet exposed to acid, alkaline solution,salt,cooling lubricant or deleterious gas is usually protected by a surface coating. For NdFeB material, it is easy to erode by high humidity or dew.

Protection from magnetic granules:rare earth permanent magnet is a sintered magnet,so the magnetic granules on the surface are unavoidable. For some applications, for example the hard disc machine or sound coil system, the soft magnetic granules will influence the function,even damage the magnetism system. The surface protection coating could protect the permanent magnet from extra accumulation and keep its surface clean thoroughly.

Operation protection: In a certain system, the permanent magnet is usually installed by mechanical pressure. Under some conditions, the pressure install process will cause smashes. The sharp brim is insecure. So we should consider the coating for every application. We suggest the user to choose the most appropriate coating for their application.

2) Types of the protection coating:?There are two basis coatings, metal coating and organic coating. To meet special requirement of the user, we could also adopt metal/metal,metal/organic double-coating and many other special coatings.

Metal coating: Usually, the metal coating is made by electrical plating technique. In addition to standard Nickel-plating and Zn-plating, other coating is also available, if the user require.

Organic coating:The basic organic coating is epoxy. Lacquer spraying is also adoptable.

Temporary anti-corruption coating/surface passivation:For the protection in transit or storage period, this temporary coating is usually used.

Quality warranty

1) Quality management of SmCo permanent magnetic product has been approved by the China electronic component quality system (i.e. China military standard approval),GB/T9001-ISO9001 quality system, IECQ international electrotechnics committee quality assessing system, China national Exp. & Imp. Enterprise approving committee.

2) The sintered permanent magnet made from rare earth alloy is bristle, especially for the SmCo permanent component, for which the crack slimmer than a hair thread or crack brim is easy to occur. But this phenomenon won?ˉt influence the magnetic properties and mechanical characteristics greatly. For NdFeB permanent magnet, cracks are not very familiar.

3) Under the proper processing technic condition,the magnetized permanent magnetic component is usually adhered with little magnetic dust and small chips. To avoid this phenomenon, we could wipe them off manually and packed the component individually. To do this, the lead-time will be longer and the cost will be higher.

4) For the final inspection of permanent magnet, we usually adopt standard sampling method. Our sampling inspection is as per the National military standard GJB179A,inspection level class,AQL1.5.

Safety principle for manual operation of permanent magnet

1) The magnetized permanent magnets with strong magnetic field attract the iron and other magnetic matters around them greatly. Under common condition, the manual operator should be very careful to avoid any damage. Due to the strong magnetic force, the big magnet close to them takes the risk of damage. People always process these magnets separately or by clamps. In this case, we should ware the protection gloves in operation.

2) In this circumstance of strong magnetic field, any sensible electronic component and test meter may be altered or damaged. Please see to it that the computer, display and magnetic media , for example the magnetic disc ,magnetic cassette tape and video record tape etc., are far from the magnetized components, say farther than 2m.

3)The collision of the attracting forces between two permanent magnets will bring enormous sparkles. Therefore, the flammable or explosive matters should not be placed around them.

4) When the magnet is exposed to hydrogen, it is prohibited to use permanent magnets without protection coating. The reason is that the sorption of hydrogen will destroy the microstructure of the magnet and lead to the deconstruction of the magnetic properties. The only way to protect the magnet effectively is to enclose the magnet in a case and seal it