What Factors Affect the Performance of Neodymium Magnets?

In the world of magnets, it is no doubt that the NdFeB is current “King of Magnets,” possessing extremely strong magnetic performance. But did you know? From raw materials to finished products, the final performance of an NdFeB magnet is influenced by numerous factors. Today, we will take a deep look at the four key factors that affect NdFeB magnet performance.

I. Raw Material Composition

NdFeB is an alloy system composed of “Main components + Additive elements”. We can imagine the NdFeB magnet as a high-performance building under construction, with different elements playing the different roles.

（I） Main Components (over 95%):

1. Neodymium (Nd): A large number of Nd atoms act like countless small compasses aligned in the same direction, jointly generating a powerful magnetic field. Too little Nd results in weak magnetism, while excessive will produce impurities and decrease performance.

2. Iron (Fe): Fe element is the largest portion of the material. Like the steel framework of a building, it fixes the arrangement of neodymium atoms and strengthen the magnetism. Without Fe, the magnetism of neodymium atoms would be disorganized.

3. Boron (B): Although B only accounts for 1%-2%, it is crucial. Like a “glue”, it bonds Nd and Fe to form a stable crystal structure. Without it, magnetism would decrease significantly or even disappear.

（II） Additive Elements:

The main components determine the “basic magnetism” of NdFeB, but in practical applications, it is also necessary to solve the problems such as “high-temperature demagnetization,” “brittleness and easy breakage,” and “poor corrosion resistance”–this requires adding a small amount of functional elements:

1. Dy &Tb: Dy and Tb can greatly improve the Hcj (demagnetization resistance) of the magnet, making it particularly suitable for high-temperature environments. However, they are expensive and will reduce magnetic force, so we need to add precisely.
2. Co & Al: Co can increase the Curie temperature of the magnet, slowing magnetic decrease at high temperatures. On the other hand, Al can increase Hcj and reducing costs.
3. Cu & Ga: Pure NdFeB is very brittle and easily break during processing. Adding Cu or Ga can improve its toughness, making it not easy to break .
4. Ni & Zn: Nd and Fe are easily rusted. By plating a coating (such as Ni) on the surface, a dense protective layer can be formed, greatly enhancing corrosion resistance and extending the usage time of magnet.

II. Production Process

As the saying goes, “If jade is not polished, it will become useless.” The performance of magnets can not be separated from the strict production processes.

1.Powdering: Powdering is the process of melting the alloy and then crushing it into powder. The smaller the powder, the higher the coercivity..

2.Orientation and Pressing: Under a strong magnetic field, the south and north poles of each powder particle are aligned in the same direction, and then pressed into shape. This is the most critical step in determining the Br of the magnet. The stronger the magnetic field, the higher the orientation degree, and the better the magnetism.

3.Sintering and Aging: The blank is sintered into a high-density solid at high temperatures. Temperature and time must be precisely controlled. Insufficient density or large crystal grains will seriously reduce performance. Aging step can optimize the internal structure and maximize coercivity.

4.Machining: The blank is processed into specific sizes and shapes. During processing, temperature and methods must be controlled; otherwise, local overheating will cause demagnetization, and improper processing force will generate micro-cracks.

5.Surface Treatment: A high-quality coating can effectively isolate humid air and prevent internal corrosion. Low-quality coatings will quickly lead to demagnetization and corrosion.

III. Usage Environment

Even a perfect magnet will have greatly reduced performance if placed in an unsuitable environment.

• Temperature

NdFeB magnets are extremely sensitive to temperature. Although their Curie temperature is above 310℃, the actual operating temperature is lower than this. When the environmental temperature exceeds its allowable operating temperature, reversible or irreversible demagnetization will occur. Once irreversible demagnetization happens, the magnetism cannot be recovered even after cooling.

Grade		Maximum Operating Temperature	Curie Temperature
N	Normal	80℃	310℃~350℃
M	Medium	100℃
H	High	120℃
SH	Super High	150℃
UH	Ultra High	180℃
EH	Extremely High	200℃
AH	Aggressively High	230℃

Countermeasure: Select grades with higher coercivity (Hcj) and better temperature resistance (such as UH, EH, and TH series) based on the actual operating temperature.

• Humidity

NdFeB has tiny holes inside. In a humid environment, water and oxygen will entering these holes, causing the magnet to be rusted and declining the magnet performance.

Countermeasure: It is a useful way to protect the magnet with high-quality surface coatings (such as Ni-Cu-Ni plating) and store it in a dry environment.

• External Magnetic Field

The magnetic domains will change directions when the magnet are placed in a strong, opponent magnetic field. This will weaken the magnet’s performance.

Countermeasure: Design the magnetic circuit precisely, and choose high grade magnet to against external interference..

• Physical Impact

NdFeB magnets are both hard and brittle. Shock can easily cause them to crack or even break. Even tiny cracks will become the starting point of decreasing the magnet performance.

Countermeasure: Using foam when transport and install.

IV. Size and Shape

The shape and size of a magnet directly affect its magnetic performance.

Size: Generally speaking, for magnets of the same grade, the larger size will generate the stronger magnetic force.

Shape: Block or disc magnets have a more concentrated and uniform magnetic field, while the irregular shapes may cause disordered magnetic field.  

Therefore, it is crucial to carefully design the size and shape of the magnet based on the applications.

To Summarize

High-quality raw materials and strict production progress together create high-performance NdFeB magnets. During use, providing a suitable operating environment (avoid high temperatures, humidity, strong reverse magnetic fields, and shocks) and plating a high-quality coating are the keys to ensure the long-term stability of magnet performance.

We hope this article helps you better understand and use this powerful magnet. If you have any questions, please leave a comment for discussion!