Are rare earth magnets permanent magnets?

The answer is a definitive Yes: Rare Earth magnets are a specific and highly specialized type of permanent magnet. In fact, they represent the absolute peak of commercially available permanent magnetism, generating significantly stronger and more stable magnetic fields than any other class of magnet.

To fully appreciate their power and permanence, it helps to understand the two main categories of magnets and where Rare Earth magnets fit into this classification.

The Two Worlds of Magnetism

Magnets are broadly divided into two main categories based on how they maintain their magnetic field:

1. Electromagnets: These require a continuous external electrical current to generate a magnetic field. When the current is turned off, the magnetism disappears.

2. Permanent Magnets: These materials retain their magnetic field naturally once they have been magnetized. They do not require any external power source to maintain their force.

Rare Earth magnets fall squarely into the permanent magnet category, alongside older, less powerful materials like Ceramic (Ferrite) and Alnico.

Why Rare Earth Magnets are "Super" Permanent

The term "Rare Earth" refers to the elements used in their composition, primarily Neodymium (NdFeB) and Samarium Cobalt (SmCo). These elements possess unique atomic structures that give them extraordinary magnetic properties, which are measured by three key parameters:

1. High Remanence ( B_r )

Remanence is a measure of the magnetic field remaining in a material after the external magnetizing force has been removed. Rare Earth magnets exhibit extremely high $B_r$ values, meaning they retain a massive amount of magnetic strength compared to conventional magnets. This is the source of their incredible pulling power.

2. High Coercivity ( H_ci )

Coercivity measures the material's resistance to demagnetization. Rare Earth magnets boast superior coercivity, making them incredibly resistant to external influences like heat, stray magnetic fields, or shock. This high resistance is what gives them their superior permanence—they hold onto their magnetic alignment stubbornly.

3. High Energy Product ( (BH)_max )

This is the ultimate measure of a magnet's strength and is derived from the remanence and coercivity. Rare Earth magnets have a dramatically higher energy product than all other materials, meaning they can deliver far greater magnetic force for their size.

The Two Dominant Rare Earth Types

The world of Rare Earth permanent magnets is dominated by two specialized alloys:

Neodymium Iron Boron (NdFeB): These are the strongest magnets available today. They are prized for delivering the maximum possible magnetic force in the smallest, most compact designs, making them indispensable in electronics, hard drives, and wind turbine generators.

Samarium Cobalt (SmCo): While slightly less powerful than Neodymium, SmCo magnets offer superior stability. They are the go-to choice for applications involving extreme heat (up to 350°C or 662°F ), such as aerospace and high-performance motors, because they resist demagnetization at temperatures that would cause Neodymium magnets to fail.

In conclusion, Rare Earth magnets are not just permanent magnets; they are the highest-performing permanent magnets in existence, enabling the miniature, powerful technologies that define the modern world.