What are the Principal Properties of a Permanent Magnet?

Permanent magnets are identified by the following principal magnetic properties:
Maximum value of energy product (BH)max, in unit of MGOe or J/m;
Residual induction Br, in unit of Gs or T;
Coercive force Hcb, in unit of Oe or A/m;
Intrinsic coercive force Hcj, in unit of Oe or A/m.

The measurement of the principal magnetic properties is made in a closed magnetic circuit tester by commonly accepted procedures. The minimum magnet volume of a sample used to measure these magnet properties shall be one cubic centimeter and the smallest dimension shall be at least 5 mm. The performance of a permanent magnetic circuit depends on the dimensions and the dimensions and the properties of all the components of the circuit.

What is Magnetic Field Strength?

Magnetic field is a physical phenomena induced by the motive electric charges in their surrounding space. Magnetism of materials arises from two atomic sources: the spin and orbital motions of electrons. Therefore, the magnetic characteristics of a material may change as a function of alloying constitution. Magnetic field strength is the measure of the vector magnetic quantity that determines the ability of an electric current, or a magnetic body, to induce a magnetic field at a given point, denoted as H, measured in A/m or Oe.

What is the Residual Induction of a Permanent Magnet?

The residual induction is any magnetic induction that remains in a magnetic material after removal of an applied saturating magnetic field, measured in gauss or tesla, denoted as Br or Jr. Residual induction is also known as magnetic remanence.

For rare earth permanent magnets such as Sm-Co and Nd-Fe-B, with the increasing of the reverse applied field H, the magnetic induction B decreases linearly in the second quadrant of demagnetization curve. Thus, any value of J or B on the second quadrant of demagnetization curve must be less than Br or Jr. This can also be comprehended as the material intrinsic magnetic polarization J cannot increase along with the inversely increased magnetizing force H.

What is the Coercive Force of a Permanent Magnet?

The coercive force of a permanent magnet is equal to the demagnetizing force to reduce the residual induction to zero in a magnetic field after magnetizing to saturation, measured in Oe or A/m, denoted as Hc or Hcb. That is, when the external applied demagnetizing field exactly reaches Hcb, the magnet has no apparent magnetic flux any more.

What is the Intrinsic Coercive Force of a Permanent Magnet?

The intrinsic coercive force of a magnetic material indicates its resistance to demagnetization. It is equal to the demagnetizing force, which reduces the magnetic polarization in the material to zero after the magnets is magnetized to saturation, measured in Oe or A/m, denoted as Hcj.

The vector sum of the magnetic dipole moments in the material is not zero, and the magnet is not totally demagnetized. When the demagnetizing force is removed at this time, the apparent magnetic induction of the magnet will spontaneously regained. So we designate Hcj as the intrinsic coercive force to distinguish it from the coercive force Hcj. It is only when the demagnetizing force reaches up to Hcj, is the magnet totally demagnetized.

What is the Energy Product of a Permanent Magnet?

The 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, measured in MGOe or J/m3. The product of magnetic induction Bd for ordinates and magnetic field Hd for abscissa is defined as energy product and denoted as (BdHd). The energy product of a permanent magnet that we commonly refer to is the maximum value (BH)max that can be obtained on the demagnetization curve.

Questions of Neodymium Mangets  What are neodymium magnets? Are they the same as “rare earth”?

Neodymium magnets are a kind of the rare earth magnets. They are called “rare earth” because neodymium is a member of the “rare earth” elements on the periodic table. Neodymium magnets are the strongest of the rare earth magnets and are the strongest permanent magnets in the world.

What are neodymium magnets made from and how are they made?

Neodymium magnets are actually composed of neodymium, iron, boron and other elements. The powdered mixture is pressed under great pressure into molds. The material is then sintered in vacuum furnace, and then ground or sliced into the desired shape. Coatings are then applied if required. Finally, the magnets are magnetized, inspected and packing before shipment.


What does the “N rating”, or grade, of the neodymium magnets mean?

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 N42 has a Maximum Energy Product of 42 MGOe. Generally speaking, the higher the grade, the stronger the magnet.

Do I have to worry about temperature with neodymium magnets?

The working temperature of NdFeB magnet is from 80 to 230°C. NormallyN35-N52 is 80°C, M series is 100°C, H series is 120°C, SH series is 150°C, UH series is 180°C, EH series is 200°C, AH series is 230°C. If the environment temperature is over the rated range, the magnetic property will be affected. Please check the demagnetization curve graphic for the details of each Grade.

What are the size limitations on manufacturing neodymium magnets?

Because of the manufacture equipments constraint, there is a certain limit range of the dimensions and the mechanism accuracy of magnets. Please check the Geometry and machining limits in our resource center.

Are your Neodymium Rare Earth Magnets RoHS compliant?

Yes, our magnets are fully RoHS compliant, meeting the European Parliament Directive entitled “Restrictions on the use Of Hazardous Substances” (RoHS).

What is the characteristic for the smco magnet?

SmCo magnets offer good thermal stability; they are resistant to corrosion and resistant to demagnetization. They are hard and brittle and may chip or break if dropped.

What are smco magnets made from and how are they made?

SmCo magnets are made of an alloy of samarium and cobalt. Its production methods is similar with Neodymium magnets: powder metallurgy manufacture, powder – pressing – sintered – machining – inspection – packing – shipment.

What is the different between SmCo5 and Sm2Co17?

SmCo5 is made up of approximately 50% samarium and 50% cobalt, and offers 16 MGOe (energy product) to 22 MGOe. It has a maximum recommended operating temperature of 250°C, and requires lower field strengths than 2:17 materials to magnetize.

Sm2Co17 is composed of about 50% cobalt, 25% samarium, 5% copper, 18% iron, 2% hafnium or zirconium, offering 24 MGOe to 32 MGOe. The 2:17 series has a maximum operating temperature of 350°C.

Whether Samarium Cobalt magnets require plating or not?

Samarium cobalt magnets are resistant to corrosion therefore coatings are not generally required for SmCo magnets. We also can offer coatings such as Ni, Zn, or Epoxy for corrosive environment or special requests.

What is the characteristic for the AlNiCo magnet?

AlNiCo magnet has good stability in high temperature applications, and a maximum working temperature of approximately 550°C. And it has high residual induction and has very strong flux output. Alnico magnets may be ground to size but not by conventional machining for low coercive (more subject to demagnetization); compared to ceramic and rare earth materials.

What is the characteristic for the Hard Ferrite magnet?

Hard ferrite magnet offer economical magnet power for price sensitive applications when you need low cost, good holding strength and great value. They are a dark charcoal grey in color, and do not appear metallic. Hard ferrite magnet is not suited for high temperature applications (over 250°C).

Why are most neodymium magnets plated or coated?

Neodymium-Iron-Boron magnets contain 60% iron and 30% neodymium, which are prone to corrosion. So the effective protection of the coatings is required for Neodymium magnets.

What is the difference between the different plating and coatings?

Please find the difference between different coatings in Surface Treatment of Neodymium Magnets.

What is the thickness of the nickel (Ni-Cu-Ni) plating?


Does the plating or coating weaken magnets’ strength?

Since Nickel is a ferromagnetism metal, the magnetic performance will be influenced by he Ni coating, smaller the size, larger the influence. Other coating won’t be affective to the magnetic property.

Do the magnets must be coated?

Not necessary. SmCo, Ferrit and Alnico have a good corrosion resistance, they don’t need a coating.

How to buy magnets from AIC Magnetics Shanghai?

You can purchase the magnets you need from AIC through the following 5 steps:
1. Inquiry: You can send us an inquiry to us via email, phone and fax.
2. Quotation: We will send you a quotation according to your requirement.
3. Order: After you confirm the prices, please pay the prepayment according to the invoice we send you.
4. Production: We will arrange the production after we receive the prepayment.
5. Delivery: We will deliver the order by the contract, providing the relative documents including test report, packing list, etc.

How to get a quote from AIC?

You can reach us by the following way
– Email: sales@aicmag.com
– Phone: 86-21-64935761
– Fax: 86-21-64935765
We will give you a specific reply within 24 hours (Monday to Friday).

I only need a few pieces of magnets, can I buy them from AIC?

Sorry, we don’t do retail business.

Can I get free samples?

We are glad to provide samples for your quality confirm. But the manufacture cost will be high for the small quantity. Usually, we will charge you a certain amount as sampling cost. Please don’t worry, it won’t be expensive, and will be return to you in the following order.

What is the Mould Fee?

We need to make a mould and magnetizing holding-set for the special shape magnets, such as arc. So we will charge you a certain amount of mould fee, but it will be return to you in the following order.

How much is the minimum order quantity?

MOQ: US$200.00 per order.

What is the delivery time?

The common delivery time for the magnetic material is as followed:
– NdFeB / SmCo: 20-25 Days
– Ferrite / AlNiCo: 30-35 Days
We will give you a precise delivery date according to the specific quantity, requirements and the manufacture condition.

How to pay the order?

The acceptable payment term is T/T and L/C. We also offer a credit account to our longtime cooperated clients.

How much are my shipping costs?

We will offer you a quotation, depending on your location and the order amount, delivered by sea, air or express for your reference.

How can I know how about the goods are, good or not?

We will supply the detailed test report, including dimension inspection and magnetic property test. Also, we will send you the photo of the products’ out-looking and packaging.

How can the magnets be protected from damage during shipment?

Please don’t worry, our magnets are all well-packaged before delivery, avoiding all the risks during the transport.
– Card Tray
– Foam Case
– Carton Box
– Wooden Pallet