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Magnetic Materials Overview
16/03/2014
What Magnet Materials Can I Choose From?
There are basically five families of magnetic materials you can choose from. These are, in order of increasing magnetic strength, the Flexible, Ceramic, Alnico, Samarium, and Neodymium types. The table below summarizes the properties of each type to help you decide what you might need.
| Magnet Material Type | Relative Cost* | Relative Strength** | General Comments | Most Popular Shapes | Typical Applications |
| Flexible | 1 | 1 | Material is like rubber - can be bent, coiled, and twisted. Easy to cut with knife or scissors. Material is a dark brown in color. | Strips - up to 3" wide by 400 feet long. Typical thickness is 1/16". Sheets - typically 24" wide by 100 feet long. Most popular thicknesses are 0.020" and 0.030". Both strip and sheet material is available with double-sided adhesive tape for easy application to products. | Crafts, labeling, signs, visual displays, premiums, magnetic calendars, business cards, etc. |
| Ceramic | 2 | 3 | Most widely used magnet material - low cost yet relatively high strength. Material is hard and brittle, dark gray in color. | Discs, Rings, Rectangles, Arc Segments. Wide range of sizes available. Most popular discs are about 3/4" diameter x 3/16" thick. | Crafts, holding, latches, toys, motors, etc. |
| Alnico | 20 | 5 | Older material, still used primarily in technical applications. Can be used at very high temperatures - up to 1,000�F. When machined, looks like steel. | Discs, Rods, Bars, Horseshoes, etc. | Meters, specialized holding, high temperature applications. |
| Samarium Cobalt (SmCo) | 70 | 25 | A "Rare Earth" type of magnet with high magnetic properties. Very brittle, but can be safely used at temperatures up to 500�F. | Discs, Rectangles, Rings | Generally more technically advanced applications |
| Neodymium Iron Boron, also known as "Neo" (NdFeB) | 35 | 40 | A "Rare Earth" type of magnet with the highest magnetic properties. Not as brittle as SmCo, but should not be used at temperatures above 300�F without special design considerations. May corrode easily under certain conditions, therefore best to protect by plating or coating. | Discs, Rectangles, Rings | Neo magnets are extremely powerful, and becoming more affordable for non-technical applications such as holding, magnetic jewelry, clasps, etc. |
*Relative Cost - this is an arbitrary number where the cost of Flexible magnet material is given a rating of 1, and other materials are compared to it.
** Relative Strength - this is also an arbitrary number, where the strength of Flexible magnet material is given a rating of 1, and other materials are compared to it.
In addition to the families noted above, there are various grades within each family. For most non-technical applications, the grade is not terribly important. The magnets listed on the MagnetShop.com site are chosen for economy and for general applications.
Which are the strongest magnets?
The most powerful magnets available today are the Rare Earths types. Of the Rare Earths, Neodymium-Iron-Boron types are the strongest. However, at elevated temperatures (of approximately 200 degrees C and above), the Samarium Cobalt types can be stronger that the Neodymium-Iron-Boron types (depending on the magnetic circuit).
How are magnets rated?
Magnets are characterized by three main properties. These are:
- Residual Induction (given the symbol Br, and measured in Gauss). This is an indication of how strong the magnet is capable of being.
- Coercive Force (given the symbol Hc, and measured in Oersteds). This is an indication of how difficult it is to demagnetize the magnet.
- Maximum Energy Product (given the symbol BHmax, and measured in Gauss-Oersteds). This is an indication of what volume of magnet material is required to project a given level of magnetic flux.
What are the properties of commonly used magnet materials?
Here are the three important properties that characterize magnets for some of the most common magnet materials used today.
How can I use this information?
Given a magnet size, you can estimate how much magnetic flux different materials will project at a given distance or you can use this information to compare one material to another.
Examples:
How much more flux will a Neo 35 project as compared to a Ceramic 5 of the same dimension at a given distance? Simply divide the Br of Neo 35 by the Br of Ceramic 5 (12,300/3,950) to get 3.1. This means that the Neo 35 would give you 3.1 times the flux a Ceramic 5 the same size would at a given distance.
Given a certain flux required at some fixed distance from the magnet, you can use this information to estimate what magnet volume will be required for different magnet materials.
For example, what volume of a Ceramic 5 magnet would give the same flux as a Neo 35 magnet at a given distance? Simply divide the BHmax of Neo 35 by the BHmax of Ceramic 5 (35/3.6) to get 9.7. This means that the volume of the Ceramic 5 magnet would have to be 9.7 times that of the Neo 35 magnet to give you the same flux.
What are the maximum recommended operating temperatures for different magnet materials?
The maximum temperature that a magnet may be effectively used at depends greatly on the magnetic circuit the magnet is operating in. Shown here are approximate maximum operating temperatures for the various classes of magnet material. At temperatures close to those listed here, special attention may be needed in order to ensure that the magnet will not become demagnetized.
specialized in manufacturing all kinds of rare-earth permanent magnets, According to the customers request, we can produce all kinds of NdFeB magnets with different complicated shapes and get them magnetized with multi-poles. The products are widely used in motor, micromotor, computer, instrument, car, motorcycle, amera, watch, HiFi, electric appliances, office automation, toy, magnetic therapy and other fields of daily life.