Have you ever seen a raw neodymium-iron-boron (NdFeB) magnet straight out of the sintering furnace? Dark black, heavy, and substantial in your hand. Yet if you bring it close to an iron nail, something surprising happens—it doesn’t attract the nail at all.

This isn’t a defect or a quality issue.

In fact, permanent magnet materials possess virtually no magnetism the moment they are manufactured. The remarkable magnetic force that firmly attracts iron components, drives motors, and enables speakers to produce sound is not innate; it is imparted later.

So where does this magnetism come from, and at what stage does it enter the magnet?

The answer lies in the microscopic world.

1. Where Does Magnetism Come From? — The “Tiny Compass Needles” of the Microscopic World

To understand why magnets acquire their magnetism only after production, we must first grasp a key concept: magnetic domains.

In magnetic materials such as neodymium-iron-boron (NdFeB), ferrites, and samarium-cobalt, every atom generates a tiny magnetic moment due to the spin of its electrons. You can imagine each of these as an extremely miniature compass needle. The magnetic moments of adjacent atoms spontaneously align in parallel, forming small, locally ordered regions known as magnetic domains. Within each domain, the magnetic moments point in the same direction, creating a localized magnetic field. However, the magnetization directions of different domains are randomly distributed, causing them to cancel each other out.

The result is that, on a macroscopic scale, the material exhibits virtually zero net magnetism.

This explains why a freshly sintered NdFeB blank shows no reaction when brought near a piece of iron. The material itself is not flawed; rather, the internal “tiny compass needles” are still in disarray. Magnetization is the command that orders all these tiny needles to march in unison.

2. From Raw Materials to Semi-Finished Products — The Manufacturing Journey of NdFeB Magnets

The production of neodymium-iron-boron (NdFeB) magnets typically involves seven core processes:

1. Melting and Strip Casting: Raw materials such as neodymium, iron, and boron are mixed according to a specific formula and melted at high temperatures in a vacuum or inert atmosphere. The molten alloy is then rapidly solidified using strip casting technology to produce uniform alloy flakes.

2. Hydrogen Decrepitation and Milling: The alloy flakes are embrittled through hydrogen treatment and then ground into micron-sized powder (approximately 3–5 μm) using a jet mill. The finer the powder, the higher the final magnetic performance.

3. Orientation and Compacting: The powder is pressed into shape within a mold while an external magnetic field is applied. This step involves a key concept: orientation. While related to subsequent magnetization, orientation is fundamentally different—a distinction that will be clarified later in this article.

4. Sintering and Aging: The compacted powder is sintered at high temperatures in a vacuum furnace, causing the particles to fuse into a dense bulk material. It then undergoes aging heat treatment to optimize the grain boundary structure. The product resulting from this stage is commonly referred to as the “blank”or “green body.”

5. Machining: The blanks are processed via wire cutting, grinding, and other methods to achieve the precise dimensions and shapes required by customers.

6. Surface Treatment: Since NdFeB magnets are highly susceptible to oxidation and corrosion, they must undergo surface treatments such as nickel plating, zinc plating, or epoxy resin coating to ensure durability and service life.

7. Magnetization: The final step—and the core focus of this article. A magnetizing machine applies a strong pulsed magnetic field to the finished product, truly imparting the practical magnetic properties that make the magnet functional.

Magnetization is the core process in the entire production flow that imparts actual magnetic properties to the magnet. It works by having the capacitor in a magnetizing machine discharge instantly, generating a pulsed magnetic field that is extremely short in duration but exceptionally high in intensity.

This magnetic field must be strong enough to exceed the material’s intrinsic coercivity (Hcj). Only then can the chaotic magnetic domains within the material overcome their inherent “inertia,” undergo irreversible flipping, and align uniformly in the same direction. After the pulsed magnetic field is removed, the domains rely on the material’s own magnetocrystalline anisotropy to stably maintain this new ordered state. This is the source of remanence (Br) and marks the moment the magnet truly “awakens.”

A Question: Since a magnetic field is also applied during the “Orientation and Compacting” stage, doesn’t that mean the powder particles are briefly magnetized at that moment? Does this imply that the magnet actually “carries magnetism” before sintering?

Answer: During the orientation process, the magnetic field does indeed cause the powder particles to exhibit a temporary degree of magnetism. If you were to bring the compacted green body close to iron powder at this stage, you would observe a slight attractive force.

However, the purpose of orientation is to use an external magnetic field to align the crystal axes of each powder particle along the direction of the field, thereby locking this “directionality” into the crystal structure during sintering. This process determines the upper limit of the magnetic performance the magnet can achieve during subsequent magnetization.

This temporary magnetism does not persist. The sintering temperature for NdFeB exceeds 1000°C, which is far above its Curie temperature (approximately 310–340°C). Under such intense thermal energy, microscopic thermal motion completely disrupts the existing alignment of magnetic domains, causing the material to transition from a ferromagnetic state to a paramagnetic state. Therefore, the moment the blank emerges from the sintering furnace, it remains a non-magnetic metal block.

Orientation grants the potential; only magnetization realizes that potential into usable magnetism. Orientation sets the ceiling, while magnetization ensures its achievement. Each plays a distinct and indispensable role.

Conclusion: A magnet’s magnetism is not innate.

From a microscopic perspective, it is the transition of magnetic domains from chaos to order. From a manufacturing standpoint, it is the “command” issued by the strong pulsed magnetic field of the magnetizing machine. Before this final step, no matter how many precise processes the material has undergone, the magnet remains silent to the outside world.

Magnetization is the moment it awakens from its slumber.