What Is the Strongest Magnetic Material?

Magnets are a fundamental part of our daily lives, operating in countless devices. From refrigerator doors to advanced machinery, their influence is widespread. Magnetism is a natural force that allows certain materials to attract or repel each other, generating a magnetic field. This article explores magnetic strength and identifies the strongest material.

Understanding Magnetic Strength

Magnetic strength is not a single, simple measurement but rather a combination of properties that determine a magnet’s performance. One property is remanence (Br), the magnetic field remaining within a material after an external field is removed. It indicates the magnet’s residual magnetism and helps measure the strongest magnetic field a permanent magnet can produce.

Another property is coercivity (Hcj or Hcb), which measures a magnet’s resistance to demagnetization. Higher coercivity means the magnet is more difficult to demagnetize, maintaining its properties even when exposed to opposing magnetic fields or temperature changes. Coercivity is the magnetic field strength required to reduce a material’s magnetization to zero.

The most comprehensive measure for permanent magnets is the maximum energy product (BHmax). This value represents the maximum energy a magnet can deliver to an external magnetic circuit. It combines remanence and coercivity, indicating the magnet’s overall energy density per unit volume. A higher BHmax signifies a stronger magnet for its size.

Neodymium Magnets: The Strongest Permanent

Neodymium magnets, specifically those made from Neodymium-Iron-Boron (NdFeB) alloys, are currently the strongest type of permanent magnet available commercially. These magnets were independently developed in 1984 by General Motors and Sumitomo Special Metals, driven by the need for more affordable alternatives to samarium-cobalt magnets. Masato Sagawa of Sumitomo Special Metals is credited with their discovery.

Neodymium magnets boast an exceptionally high maximum energy product (BHmax) compared to other permanent magnets. Their BHmax can range from 200 to 400 kJ/m³, significantly higher than Alnico magnets (10 to 88 kJ/m³). This superior energy product allows them to generate a greater magnetic field in a smaller size.

Neodymium magnet strength is indicated by grades like N35, N42, or N52. The number signifies the magnet’s maximum energy product in Mega-Gauss Oersteds (MGOe). A higher number, such as N52, indicates greater magnetic strength and is generally considered the strongest readily available grade.

The Science of Neodymium’s Power

The extraordinary strength of neodymium magnets stems from their unique atomic structure and composition. They are primarily composed of neodymium, iron, and boron, forming a specific tetragonal crystalline structure known as Nd2Fe14B. This particular arrangement of atoms is crucial to their magnetic properties.

Rare-earth elements like neodymium possess electron configurations that contribute to strong magnetic moments. Within the Nd2Fe14B crystal structure, these atomic properties lead to high magnetic anisotropy. This means the material preferentially magnetizes along a specific crystal axis and resists demagnetization in other directions.

During manufacturing, the alloy’s microcrystalline grains are aligned in a powerful magnetic field, ensuring their magnetic axes point in the same direction. This alignment, combined with the material’s high magnetic saturation, results in both high remanence and high coercivity. The resistance of the crystal lattice to changing its direction of magnetization provides the compound with its impressive demagnetization resistance.

Applications of Powerful Magnets

The exceptional strength of neodymium magnets has led to their widespread use across modern technologies and industries. They are integral components in electric motors for electric vehicles, robotics, and drones, allowing for efficient energy conversion and compact designs. These magnets also play a role in computer hard drives, enabling precise and rapid data reading and writing.

In audio equipment, neodymium magnets are used in headphones and speakers to produce clear sound from small devices. Medical imaging benefits from these powerful magnets, particularly in MRI machines, where they help generate strong magnetic fields for detailed body scans.

Neodymium magnets also contribute to renewable energy, used in generators in many wind turbines. Their high energy product allows for efficient electricity generation, reducing the need for gearboxes and improving reliability in these large systems. Beyond these high-tech applications, powerful magnets are also used in simpler items like magnetic fasteners and closures due to their strong attractive force.