Table OF CONTENTS

1. Permanent Magnet Materials
Permanent Buy magnets are used in the following major groups: acoustic transducers, motors and generators, magneto mechanical devices, and magnetic field and imaging systems. You will find permanent magnets in many products, such as televisions, telephones, computers, audio systems and automobiles.
The permanent magnet family consists, in general terms, of non-rare earth permanent magnets and rare earth magnets. The non-rare earth magnets include Alnico (Aluminum-Nickel-Cobalt) magnets and Ceramic (Strontium and Barium Ferrite) magnets. Rare earth magnets include Sm-Co (Samarium-Cobalt) magnets and NdFeB (Neodymium-Iron-Boron) magnets.
Although non-rare earth magnets are used in the majority of these applications due to their economic cost, rare earth permanent magnets have many distinguishing characteristics, such as a large Maximum Energy product, (one performance index for permanent magnets). Dozens of magnetic materials which contain rare earth have been developed recently. Two major families of rare earth permanent magnets, SmCo magnets and NdFeB magnets, have been widely used in a variety of applications. Each family has its own advantages and disadvantages.
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2. NdFeB Magnets
NdFeB magnets have a higher Maximum Energy product,(BH)max, than Sm-Co magnets. (BH) max of NdFeB can easily reach 30 MGOe and even goes up to 48 MGOe. NdFeB magnets can replace Sm-Co magnets in most cases, especially where operating temperature is less than 80 degrees Centigrade. The temperature stability of NdFeB is not as good as Sm-Co magnets. Magnetic performance of NdFeB magnets will deteriorate rapidly above about 180 degrees Centigrade. Compared to SmCo magnets, the corrosion and oxidation resistance of NdFeB is relatively low. Sintered NdFeB permanent magnets are made with several steps. At first, a NdFeB alloy is formulated based on the properties of final permanent magnets supposed to reach. The alloy is produced in a vacuum furnace. Then the alloy is crushed into a powder form. Sintered NdFeB permanent magnets are formed by powder metallurgical process. These magnets can be die pressed or isostatically pressed. During the pressing process, magnetic fields are applied with assistance of specially designed fixture to align magnetic "domains" and optimize the magnetic performance of these magnets. Then pressed magnets are placed into a furnace under protective atmosphere for sintering. After sintering the magnet shape is rough, and need to be machined and ground to achieve desired shape and size. A surface coating is usually applied on NdFeB magnets. Zinc or nickel coating is common used as a protective layer. Other materials such as cadmium chromate, aluminum chromate, tin or polymer (epoxy) are also used for this purpose. Both NdFeB and Sm-Co magnets can be made either in sintered or polymer-bonded magnets. The polymer (such as epoxy)-bonded magnets can be produced with close tolerances off tool, with little or no finishing required. Stamford Magnets supplies polymer-bonded NdFeB permanent magnets made by both compression moulding and injection moulding. The sintered magnets usually require some finishing operations in order to hold close mechanical tolerances. The sintered magnets, however, provide better magnetic properties than bonded magnets.Buy magnets

A: Sintered NdFeB Magnet properties

1. Use of sintered NdFeB permanent magnets, as the piece part magnet or as it's assembly, made by non-licensee is prohibited by the patent Law of the United States of America. All of sintered neodymium-iron-boron (NdFeB) permanent magnets, which Stanford Magnets Company supplies, are licensed. 2. The grades listed are only a portion of the products we carry; please contact us for the grade you need 3. The data listed are the typical properties, and the data in parentheses are the minimum values 4. Some general properties: Density: 7.4 -7.6; Hardness: 600 {Hv}

B: Properties of Polymer Bonded NdFeB Magnets by Compression Moulding,Buy magnets

C: Properties of Polymer Bonded NdFeB Magnets by Injection Moulding

3. SmCo Magnets
Two common compositions of SmCo magnets are Sm1Co5 and Sm2Co17. Generally, the cost of Sm-Co magnets is higher than NdFeB magnets. As a big advantage, Sm-Co magnets can operate at higher temperatures up to 300 degrees Centigrade. Sm-Co magnets are widely used in applications in which higher operating temperature and higher corrosion and oxidation resistance are crucial.

A: Sintered SmCo Magnet properties

B: Bonded Sm-Co Magnet properties

4. Alnico:
Alnico magnetic material is an alloy of aluminum-nickel-cobalt which possesses an excellent temperature stability and high residual induction . However, its low coercive force limits its applications in many cases. Casting and sintering are two major processes used to manufacture the Alnico magnets. Alnico magnets with complex shapes may be manufactured by casting. However, once the Alnico magnets are formed, it is difficult to machine or drill them due to the hard and brittle mechanical properties of Alnico.

A: Casted Al-Ni-Co Magnet properties

B: Sintered Al-Ni-Co Magnet properties

5. Ceramic (Hard Ferrite)
Ceramic magnets are composed of iron oxide, barium and strontium elements. This class of magnets has a higher magnetic flux density, higher coercive force, and higher resistance to demagnetization and oxidation compared to other non-rare earth permanent magnets. The biggest advantage of such magnets is their low cost, which makes the hard ferrite magnets very popular in many permanent magnet applications. Due to their ceramic nature, ferrite magnets are very hard and brittle. Special machining techniques must to be utilized for these magnets.

Ceramic (Hard Ferrite) permanent Magnets

6. Flexible and plastic Magnets
Flexible magnets can be either isotropic and anisotropic. The anisotropic flexible magnets are made by extrusion or injection. properties such as high elasticity, flexibility and machinability make these magnets a favorite candidate for many permanent magnet applications in industry and in home appliances.

Flexible permanent Magnets

REFERENCE BOOKS

Following books may be helpful for you in designing and selecting permanent magnet materials.

1. Permanent Magnet Design and Application Handbook, by Lester R. Moskowitz; published by Krieger publishing Company, Malabar, Florida; ISBN 0-89464-768-7

2. Permanent Magnet Materials and Their Application, by Dr. peter Campbell

3. Standard Specifications for permanent Magnet Materials, published by Magnetic Materials producers Association; (312) 201-0101, (312) 201-0214 (fax)

4. permanent Magnet Guidelines, published by Magnetic Materials producers Association; (312) 201-0101, (312) 201-0214 (fax)

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