Br, residual induction
The measure of magnetic capability of the magnet. Br only exists in a closed circuit. This is like a fully charged battery.
Br is reported in Gauss, kiloGauss, Tesla or miliTesla
The higher the value of Br, the smaller is the required magnet cross sectional area to perform a specific task
Hcb, normal coercivity
The measure of the field required to drive B to zero. At this point the magnet is not fully demagnetized, but will recoil to some "B" when the field is removed or when the load line increases. Operating at Hc is like short circuiting a battery for a short time.
Hcb is reported in Oersteds, kiloOersteds, Ampere / meter
Hcj, intrinsic coercivity
The measure of the magnet's resistance to demagnetization, the demagnetization field required to fully demagnetize. At this point the magnet is demagnetized inside the magnet. This is like applying a reverse voltage to a battery or shorting it for a long time.
Hcj is reported in Oersteds, kiloOersteds or Ampere/meter
The higher the value of Hcj, the smaller is the required magnet thickness (Lm) to withstand a specific demagnetizing influence.
(BH)max, max. energy product
The point on the demag curve where the function of B*H maximizes is theoretically the most efficient operating point.
B*H is referred to as the energy product.
Energy product is reported in Mega Gauss Oersteds or Joule/meter3.
It is generally a figure of merit, used for rapid comparison of different magnet materials.
Air gap is Space between the poles of a magnet in which there exists a useable magnetic field.
When does Sm-Co require coating?
Sm-Co is typically plated for medical applications to give a "sealing" coat of nickel. This is extra insurance against the rare flake of iron. Nickel can be good insurance against such flaking, by making the surface tougher. It also protects the magnet from sterilizing chemicals and other contaminates.
Why are rare earth magnets so expensive?
In the case of the rare earth magnets, the heavy metals used to enhance the magnetic properties are difficult to extract. The magnet-related elements are actually a small fraction of the lanthanides mined, so material cannot be produced in huge quantities. Since the fine powders are pyrophoric, production conditions need to be very tightly controlled, and there is a limit to the size of block that can be formed due to the pressure required. Subsequent machining of the magnets adds more cost. Because the magnets are typically very hard and brittle, grinding and slicing operations are slow.
What's the difference between Alnico, Sm-Co & Nd-Fe-B magnet materials?
Alnico is an older magnet material that still has important applications. Its maximum energy product is about 1/5 of Sm-Co materials, but it has excellent elevated temperature properties and has better corrosion resistance. Alnico can be cast into different shapes with various magnetic orientations. The rare earth Sm-Co and Nd-Fe-B magnets have high coercivity, so they do not need to be magnetized in circuit and can be used with low permeance coefficients (i.e. thin discs). These materials also lend themselves to Helmholtz coil testing due to their straight line normal curves. This also makes rare earths ideal for motors and high field dipoles. Sm-Co has a good resistance to thermal demagnetization but is brittle. Nd-Fe-B is less brittle, has poor thermal properties, and is prone to corrosion.(9)
What information should I provide when ordering?
We will help you with your order. Usually we ask for the following information.
· Material type and grade required.
· Size and shape, if available, a sketch or drawing with dimensions and tolerances.
· Max working temperature.
· Delivered magnetized or unmagnetized? Magnetization direction?
· Quantities required.
· Coating required (if any)
· Information on what you want to use the magnet for.
General information on Neodymium Iron Boron Magnet Materials
Sintered neodymium-iron-boron (Nd-Fe-B) magnets are the most powerful commercialized permanent magnets available today, with maximum energy product ranging from 26 MGOe to 52 MGOe. Nd-Fe-B is the third generation of permanent magnet developed in the 1980s. It has a combination of very high remanence and coercivity, and comes with a wide range of grades, sizes and shapes. With its excellent magnetic characteristics, abundant raw material and relatively low prices, Nd-Fe-B offers more flexibility in designing of new or replace the traditional magnet materials such as ceramic, Alnico and Sm-Co to achieve high efficiency, low cost and more compact devices.
A powder metallurgy process is used in producing sintered NdFeB magnets. Although sintered NdFeB is mechanically stronger than Sm-Co magnets and less brittle than other magnets, it should not be used as structural component. Selection of Nd-Fe-B is limited by temperature due to its irreversible loss and moderately high reversible temperature coefficient of Br and Hci. The maximum application temperature is 200 C for high coercivity grades. Nd-Fe-B magnets are more prone to oxidation than any other magnet alloys. If Nd-Fe-B magnet is to be exposed to humidity, chemically aggressive media such as acids, alkaline solutions salts and harmful gases, coating is recommended. It is not recommended in a hydrogen atmosphere.
Neodymium magnets are a member of the Rare Earth magnet family and are the most powerful permanent magnets in the world. They are also referred to as NdFeB magnets, or NIB, because they are composed mainly of Neodymium (Nd), Iron (Fe) and Boron (B).
What can Neodymium magnets do?
Magnets affect electrically charged particles and electrical conductors. Magnets have the ability transform electrical energy without losing their own energy. These effects can perform useful functions, for example:
·Electrical-to-mechanical effects are key in the function of motors, loudspeakers, and equipment that requires charged particle deflection.
·Mechanical-to-electrical effects are useful in generators, motors and microphones
·Mechanical-to-heat effects facilitate eddy current and hysteresis torque devices.
·Mechanical-to-mechanical affects, Magnetic separators, Sensors.
·Other effects of magnets include magneto-resistance and magnetic resonance.
The temperature coefficient of neodymium has triggered several grades to be developed to meet specific operating requirements. Please refer to our chart of magnetic properties to compare the characteristics of each grade. Before choosing a neodymium magnet be sure to consider your application㡯s maximum operating temperature.(13)
Neodymium magnets require extremely high magnetizing fields and particular consideration must be given to this when designing complex assemblies. Neodymium can be magnetized in any direction as long as it is aligned properly. In some instances multiple pole magnetization is not possible; when it is possible, special fixtures are required.(14)
Are there any regulations for shipping magnetized materials?
According to the United States Department of Transportation and the Office of Hazardous
Materials Safety, it is against regulations to ship a magnet by air that maintains a field of more than 0.00525 gauss measured at 4.5 meters (15 feet) from any surface of the package. This is to prevent the magnet from interfering with the operation of the aircraft's navigational compass. There are no federal regulations that restrict the shipping of magnetized materials by ground transportation. Please check with your commercial carrier for additional specifics.
What materials can be used for magnetic shielding?
In general, magnetic field attenuation is a function of the permeability of the material. A better shielding material has high permeability per weight. For metallic foil and sheet, the most efficient shielding material is the 80 Nickel family (e.g., Molypermalloy), followed by the 50 Nickel alloys (e.g., Deltamax). The economical silicon-steel foils and sheets are also good shielding material when weight is not of a major issue.(16)
How long do magnets hold their magnetic strength?
If the magnets are not subjected to external magnetic fields high enough to cause demagnetization - and/or - elevated temperatures above the advertised maximum use temperature the field will remain at or near as received. This could be expected last for the life of the application.(17)
Can magnets be made stronger?
Once a magnet is fully magnetized, it cannot be made any stronger.(18)
Can magnets that have lost their magnetism be re-magnetized?
That depends on how the magnetism was lost. Usually magnets can regain their original strength unless they've been exposed to extreme heat.(19)
Do magnets get weaker? How?
Several factors can weaken the magnetism in a magnet. If a magnet is stored close to heat, strong electrical currents, other magnets, or radiation, it can lose its strength. Additionally, high humidity can corrode neodymium magnets. Demagnetization
Rare Earth magnets have a high resistance to demagnetization, unlike most other types of magnets. They will not lose their magnetization around other magnets or if dropped. They will however, begin to lose strength if they are heated above their maximum operating temperature, which is 176F (80 C) for standard N grades. They will completely lose their magnetization if heated above their Curie temperature, which is 310F (590 C) for standard N grades. Some of our magnets are of high temperature material, which can withstand higher temperatures without losing strength.
What are magnetic poles?
All magnets have points, or poles, where their magnetic strength is concentrated. Those points are called poles. We label them north and south because suspended magnets orient along north-south planes. On different magnets, like poles repel each other, opposite poles attract. Are permanent magnets really permanent?(21)
What does 'orientation direction' mean?
Some magnets, called oriented or anisotropic magnets, have a preferred direction in which they should be magnetized. The "orientation direction," also known as an "easy axis" or "axis," is the direction that achieves its maximum magnetism. Other magnets, called unoriented or isotropic magnets, can be magnetized in any direction.(22)
What are rare earth magnets?
The term Rare Earth Magnets is 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.(23)
Coatings of Neodymium magnets
The coatings do not affect the magnetic strength or performance of the magnet.
Neodymium magnets are a composition of mostly Neodymium, Iron and Boron. If left exposed to the elements, the iron in the magnet will rust. To protect the magnet from corrosion and to strengthen the brittle magnet material, it is usually preferable for the magnet to be coated. There are a variety of options for coatings, but nickel is the most common and usually preferred. Our nickel plated magnets are actually triple plated with layers of nickel, copper, and nickel again. This triple coating makes our magnets much more durable than the more common single nickel plated magnets. Some other options for coating are zinc, tin, copper, epoxy, silver and gold. Our gold plated magnets are actually quadruple plated with nickel, copper, nickel and a top coating of gold.
Grades of Neodymium magnets
N35, N38, N42, N38SH...what does it all mean? Neodymium magnets are all graded by the material they are made of. As a very general rule, the higher the grade (the number following the 'N'), the stronger the magnet. The highest grade of neodymium magnet currently available is N50. Any letter following the grade refers to the temperature rating of the magnet. If there are no letters following the grade, then the magnet is standard temperature neodymium. The temperature ratings are standard (no designation) - M - H - SH - UH - EH. You find the temperature rating of each grade on our Specifications of Neodymium Magnets Page.
The grade, or "N rating" of the magnet refers to the Maximum Energy Product of the material that the magnet is made from. It refers to the maximum strength that the material can be magnetized to. The grade of neodymium magnets is generally measured in units millions of Gauss Oersted (MGOe). A magnet of grade N38 has a Maximum Energy Product of 38 MGOe. Generally speaking, the higher the grade, the stronger the magnet.
Rear Earth Magnets
There are two types of rare earth magnets available: Neodymium and Samarium Cobalt.
They are called rare earth because their composition elements found in the "Rare Earth" or Lanthanides portion of the Periodic Table of Elements.
Neodymium magnets (Nd-Fe-B) are composed of neodymium, iron, boron and a few transition metals. Samarium cobalt magnets (SmCo) are composed of samarium, cobalt and iron. These rare earth magnets are extremely strong for their small size, metallic in appearance and found in simple shapes such as rings, blocks and discs.
Due to their tremendously high energy level, Rare Earth magnet material is ideal for miniaturized applications. They offer high resistance to demagnetization and are recommended for applications with temperature ranges under 200oF. Raw Rare Earth magnets have a dull metallic appearance and tend to be very brittle. They can be ground, but caution must be exercised not to crush the material. Be aware of possible fire from the dust particles produced from grinding or cutting Rare Earth magnet materials.